Abstract:
System and method for implementing a link aggregation system, a protection system, and an XPIC application for an all outdoor radios system using a wireless channel operating at a license-free 60 GHz band are provided. The license-free 60 GHz band offers a wide frequency bandwidth that can support a high speed data rate up to 10 Gbps in full duplex mode, frequency reuse, and high security due to its fast oxygen absorption at 60 GHz. As such, a wireless channel operating at the license-free 60 GHz band may be used for a link aggregation system to support wireless local area network (LAN) connections with the speed up to 7 Gbps. In addition, a wireless connection operating at the license-free 60 GHz band may be used to support both XPIC application and protection system for all outdoor radios to achieve a transmission speed of up to 10 Gbps in a full duplex mode.

Description:
FIELD OF INVENTION 
       [0001]    The present invention relates generally to the field of all outdoor radios equipment used for wireless communication, and in particular, to the field of implementing a link aggregation system, a protection system, or a cross polarization interference cancellation (XPIC) application for all outdoor radios using wireless channels operating at a license-free 60 GHz band. 
       BACKGROUND 
       [0002]    The required capacity of backhaul networks grows exponentially in recent years. While copper or fiber optic based wired systems can provide data throughput of 10 Gbps or more, the microwave radio channel throughput of traditional frequency bands between 6 and 42 GHz is currently 500 Mbps or less. In order to increase the data throughput of wireless communication, link aggregation schemes are used where two or more microwave radios are connected in parallel as shown in  FIG. 1A . 
         [0003]      FIG. 1A  is an exemplary illustration of an all outdoor radios link aggregation system  100 A with a star-like wired connection. High-speed data traffic (which is typically in Ethernet format but could be in any other digital format) is connected to a first radio unit  101 A. The digital data interface module  101 A- 1  in the first radio unit  101 A splits the incoming data into two or more data streams. Each data stream has a data rate that is equal to or less than the throughput of a single microwave radio. One data stream is transmitted by the first radio unit  101 A. The other data streams are connected to the other radios such as a second radio unit  102 A and a third radio unit  103 A in the link aggregation system using high-speed digital cables (which are typically Ethernet cable but could be any other digital cable). Different radio units transmit data streams using different carrier frequencies. On the local side, the output Radio Frequency (RF) signal of each transceiver ( 101 A- 3 ,  102 A- 3 , and  103 A- 3 ) is transmitted to an antenna coupling unit (ACU)  104 , which combines them together and transmits the combined data streams to an antenna and subsequently into the air. The ACU  104  is a passive device that allows multiple transmitters to be connected to the same antenna. On the remote side, the received RF signal is delivered to a corresponding ACU that is configured to transmit the received RF signal to multiple receivers. Note that the equipment on the remote side has the same configuration as the one shown in  FIG. 1A  except that the ACUs are located on the left side and the digital data interfaces are on the right side. Different radio units are tuned on different carrier frequencies to receive one data stream. The digital data streams from some radios are connected to the digital data interface of the first radio, which combines them together to reconstruct the original data traffic and sends the data traffic to the user&#39;s equipment. In this configuration, the first radio unit  101 A (i.e., the master radio) has multiple weatherproof connectors on its enclosure, each weatherproof connector used for connecting to another radio unit in the link aggregation system. This increases the size of the all outdoor radio enclosure. Because the other radio units are usually of the same type as the first radio unit  101 A, all the other radio units will have extra outdoor connectors that are not used at the same time. Further, the installation and maintenance of multiple outdoor-rated high-speed cables between the radio units in the link aggregation system is difficult and expensive. 
         [0004]      FIG. 1B  illustrates an alternative, currently used approach of having multiple radio units daisy-chained. In this daisy-chain approach, each all outdoor radio unit splits the incoming data into two data streams: one data stream to be transmitted by the radio unit itself and having a data rate equal to or less than the throughput of the radio unit, and the second data stream, which contains the remaining data, is forwarded to the next radio unit in the chain. Using this daisy-chain approach, each all outdoor radio unit only needs one extra connector. But this daisy-chain approach causes more latency because the overall latency is determined by the longest path in the link aggregation system. 
         [0005]    In addition, wireless communication in current radio backhaul networks may be affected and deteriorated for various reasons, for example, multipath interference, hardware failure, selective path fading etc. In order to protect the wireless communication against these factors, microwave radio units may often be deployed in a one plus one (1+1) protection mode such as hot standby configuration, space diversity configuration, frequency diversity configuration, or hybrid diversity configuration. The radio units that participate in the protection configuration need to exchange data and signaling information to ensure proper operation. 
         [0006]    Currently, all outdoor radios protection system may employ a high speed digital wired connection to exchange information between the radio units. The transmission speed of the digital wired connection may be up to 1 Gigabits per second (Gbps) in full duplex mode. 
         [0007]      FIG. 1C  illustrates an exemplary illustration of an all outdoor radios protection system  100 B using a wired connection in related art. As illustrated in  FIG. 1C , a first radio unit  101 B and a second radio unit  102 B are deployed in the protection configuration. A first protection interface  108 B of the first radio unit  101 B and a second protection interface  115 B of the second radio unit  102 B are connected by an outdoor digital cable with a transmission speed up to 1 Gbps in full duplex mode. 
         [0008]    Finally, an XPIC application is often employed in current radio backhaul networks to improve the capacity of a radio frequency (RF) channel, which effectively doubles the capacity of an RF channel by allowing two microwave radio units to operate on the same frequency. One radio unit uses the vertical polarization while the other radio unit uses the horizontal polarization. Demodulator in each radio unit of the XPIC application receives, respectively, intermediate frequency (IF) signals from a local receiver and from the receiver of the other radio unit operating an opposite polarization. Demodulator uses the IF signal from the other radio to cancel the interference from the opposite polarization in the IF signal from the local receiver caused by limited antenna cross polarization discrimination. 
         [0009]      FIG. 1D  is an exemplary illustration of an all outdoor radios system implemented with an XPIC application using a wired connection in related art. As illustrated in  FIG. 1D , a first radio unit  101 C is configured to operate using the vertical polarization, and a second radio unit  102 C is configured to operate using the horizontal polarization. A first demodulator  105 C of the first radio unit  101 C uses the IF signal  116 C from the second radio unit  102 C to cancel the interference from the horizontal polarization in the IF signal  115 C from the first radio unit  101 C. 
         [0010]    When an XPIC application in combination with a protection system is employed in an all outdoor radios system, a total of six wired connections between the four radio units are required.  FIG. 1E  is an exemplary illustration of an all outdoor radios system equipped with a protection system and an XPIC application using a wired connection in related art. As illustrated in  FIG. 1E , there are two wired XPIC interconnections  233 C,  234  between a first radio unit  201 C and a second radio unit  202 C, two wired XPIC interconnections  237 C,  238 C between a third radio unit  203 C and a fourth radio unit  204 C, one wired protection interconnection  235 C between the first radio unit  201 C and the third radio unit  203 C, and one wired protection interconnection  236 C between the second radio unit  202 C and the fourth radio unit  204 C are required. 
         [0011]    However, the wired XPIC and protection connections require both the weatherproof connectors on the enclosure of the all outdoor radio units and the outdoor rated digital cables. Due to the sizes of the antennas at certain frequency bands, the installation and maintenance of the XPIC pair of the all outdoor radio units may be difficult and expensive. 
       SUMMARY 
       [0012]    In accordance with some embodiments of the present invention, a system and method for implementing an all outdoor radio link aggregation system uses a wireless channel operating at a license-free 60 GHz band that substantially obviates one or more problems due to the limitations and disadvantages of the related art. 
         [0013]    The license-free 60 GHz band offers at least the following key benefits: (i) a wide frequency bandwidth that can support a very high speed data rate ranging from 1 Gbps up to 10 Gbps in full duplex mode, (ii) frequency reuse, and (iii) high security due to its fast oxygen absorption at 60 GHz. A wireless connection operating at the license-free 60 GHz band may be used for an all outdoor radios link aggregation system to support wireless local area network (LAN) connections with the speed up to 7 Gbps, which is sufficient for the link aggregation system including up to seven microwave radio units, assuming each radio has a 500 Mbps throughput. Moreover, the replacement of the conventional wired link aggregation approach with the high data rate of the license-free 60 GHz wireless connection eliminates the high-speed outdoor-rated protection cables between radio units and the multiple weatherproof connectors for cables on the all outdoor radio units. For example, an all outdoor radio unit optimized for low latency star-like configuration needs only one connector for a 60 GHz antenna. Further, the radio installation is simplified and the maintenance cost is reduced. 
         [0014]    In an embodiment, a method is provided for implementing an all outdoor radios link aggregation system using a wireless channel operating at a license-free 60 GHz band, the method comprising the steps of: receiving an upstream user data at a first digital data interface of a first radio unit; splitting the upstream user data into at least a first sub-stream digital data and a second sub-stream digital data at the first digital data interface; transmitting the first sub-stream digital data through a first rear-end modem and a first rear-end transceiver of the first radio unit; transmitting the second sub-stream digital data to a first wireless controller of the first radio unit; encapsulating the second sub-stream digital data into a second sub-stream data packet addressed to a first destination radio unit at the first wireless controller, and transmitting the second sub-stream data packet to a first front-end modem of the first radio unit; converting the second sub-stream data packet into a first downstream data intermediate frequency (IF) signal at the first front-end modem, and transmitting the first downstream data IF signal to a first front-end transceiver of the first radio unit; converting the first downstream data IF signal into a first 60 GHz radio frequency (RF) signal, and amplifying the first 60 GHz RF signal at the first front-end transceiver; transmitting the first 60 GHz RF signal at a first 60 GHz antenna of the first radio unit; receiving the first 60 GHz RF signal at a second 60 GHz antenna of a second radio unit; amplifying the first 60 GHz RF signal, and converting the first 60 GHz RF signal into a second upstream data IF signal at a second front-end transceiver of the second radio unit, and transmitting the second upstream data IF signal to a second front-end modem of the second radio unit; converting the second upstream data IF signal into a second upstream data packet, and transmitting the second upstream data packet to a second wireless controller of the second radio unit; decapsulating the second upstream data packet at the second wireless controller, accepting the second upstream data packet if the second radio unit is the addressed first destination radio unit, and converting the second upstream data packet into a second upstream digital data; transmitting the second upstream digital data to a second digital data interface of the second radio unit; and transmitting the second upstream digital data through a second rear-end modem and a second rear-end transceiver of the second radio unit. 
         [0015]    In a further embodiment, a method is provided for implementing an all outdoor radios link aggregation system using a wireless channel operating at a license-free 60 GHz band, the method comprising the steps of: receiving at least a third sub-stream digital data at the first digital data interface and a fourth sub-stream digital data at the second digital data interface; transmitting the fourth sub-stream digital data to the second wireless controller; encapsulating the fourth sub-stream digital data into a fourth sub-stream data packet addressed to a second destination radio unit at the second wireless controller, and transmitting the fourth sub-stream data packet to the second front-end modem; converting the fourth sub-stream data packet into a second downstream data IF signal at the second front-end modem, and transmitting the second downstream data IF signal to the second front-end transceiver; converting the second downstream data IF signal into a second 60 GHz radio RF signal, and amplifying the second 60 GHz RF signal at the second front-end transceiver; transmitting the second 60 GHz RF signal at the second 60 GHz antenna; receiving the second 60 GHz RF signal at the first 60 GHz antenna; amplifying the second 60 GHz RF signal, and converting the second 60 GHz RF signal into a first upstream data IF signal at the first front-end transceiver, and transmitting the first upstream data IF signal to the first front-end modem; converting the first upstream data IF signal into a first upstream data packet, and transmitting the first upstream data packet to the first wireless controller; decapsulating the first upstream data packet, accepting the first upstream data packet if the first radio unit is the addressed second destination radio unit, and converting the first upstream data packet into a first upstream digital data; transmitting the first upstream digital data to the first digital data interface; and aggregating the first upstream digital data and the third sub-stream digital data, reconstructing a first downstream user data, and transmitting the first downstream user data. 
         [0016]    In yet another embodiment, the first sub-stream digital data is configured with a data rate equal to or less than the throughput of the first radio unit and the second sub-stream digital data is configured with a data rate equal to or less than the throughput of the second radio unit. 
         [0017]    In yet another embodiment, the third sub-stream digital data is configured with a data rate equal to or less than the throughput of the first radio unit and the fourth sub-stream digital data is configured with a data rate equal to or less than the throughput of the second radio unit. 
         [0018]    In yet another embodiment, the first radio unit and the second radio unit are configured to operate at the license-free 60 GHz band. 
         [0019]    In yet another embodiment, the first radio unit and the second radio unit are configured to connect in parallel to an ACU. 
         [0020]    In yet a further embodiment, provided is an all outdoor radios link aggregation system using a wireless channel operating at a license-free 60 GHz band, the system comprising: a first radio unit including: a first digital data interface configured to receive an upstream digital data, and split the upstream digital data into at least a first sub-stream digital data and a second sub-stream digital data; a first rear-end modem configured to receive the first sub-stream digital data, and transmit the first sub-stream digital data to a first rear-end transceiver; a first digital wireless controller configured to receive the second sub-stream digital data, encapsulate the second sub-stream digital data into a second sub-stream data packet addressed to a first destination radio unit; a first front-end modem configured to convert the second sub-stream data packet into a first downstream data intermediate frequency (IF) signal; a first front-end transceiver configured to convert the first downstream data IF signal into a first 60 GHz radio frequency (RF) signal, and amplify the first 60 GHz RF signal; and a first 60 GHz antenna configured to transmit the first 60 GHz RF signal; at least a second radio unit including: a second 60 GHz antenna configured to receive the first 60 GHz RF signal; a second front-end transceiver configured to amplify the first 60 GHz RF signal, and convert the first 60 GHz RF signal into a second upstream data IF signal; a second front-end modem configured to convert the second upstream data IF signal into a second upstream data packet; a second wireless controller configured to decapsulate the second upstream data packet, accept the second upstream data packet if the second radio unit is the addressed first destination radio unit, and convert the second upstream data packet into a second upstream digital data; a second digital data interface configured to receive the second upstream digital data; and a second rear-end modem and a second rear-end transceiver configured to transmit the second upstream digital data. 
         [0021]    In yet another embodiment, provided is an all outdoor radios link aggregation system using a wireless channel operating at a license-free 60 GHz band, wherein the first digital data interface is further configured to receive a third sub-stream digital data; the second digital data interface is further configured to receive a fourth sub-stream digital data; the second wireless controller is further configured to encapsulate the fourth sub-stream digital data into a fourth sub-stream data packet addressed to a second destination radio unit; the second front-end modem is further configured to convert the fourth sub-stream data packet into a second downstream data IF signal; the second front-end transceiver is further configured to convert the second downstream data IF signal into a second 60 GHz radio RF signal, and amplify the second 60 GHz RF signal; the second 60 GHz antenna is further configured to transmit the second 60 GHz RF signal; the first 60 GHz antenna is further configured to receive the second 60 GHz RF signal; the first front-end transceiver is further configured to amplify the second 60 GHz RF signal, and convert the second 60 GHz RF signal into a first upstream data IF signal; the first front-end modem is further configured to convert the first upstream data IF signal into a first upstream data packet; the first wireless controller is further configured to decapsulate the first upstream data packet, accept the first upstream data packet if the first radio unit is the addressed second destination radio unit, and convert the first upstream data packet into a first upstream digital data; the first digital data interface is further configured to receive the first upstream digital data, aggregate the first upstream digital data and the third sub-stream digital data, reconstruct a first downstream user data, and transmit the first downstream user data. 
         [0022]    In accordance with some embodiments of the present invention, a system and method for implementing an all outdoor radio protection system uses a wireless channel operating at a license-free 60 GHz band that substantially obviates one or more problems due to limitations and disadvantages of the related art. A wireless connection operating at the license-free 60 GHz band may be used for all outdoor radios protection system to achieve a transmission speed of up to 10 Gbps in full duplex mode, and therefore, to accommodate bandwidth needs for current microwave radio applications, and for future capacity growth. 
         [0023]    In an embodiment, a method is provided for implementing an all outdoor radios protection system using a wireless channel operating at a license-free 60 GHz band, the method including the steps of receiving a first downstream protection digital signal at a first protection interface of a first radio unit; converting the first downstream protection digital signal into a first downstream protection intermediate frequency (IF) signal at a first modulator/demodulator unit of the first radio unit; converting the first downstream protection IF signal into a first 60 GHz radio frequency (RF) signal, and amplifying the first 60 GHz RF signal at a first transceiver; transmitting the first 60 GHz RF signal at a first antenna of the first radio unit; receiving the first 60 GHz RF signal at a second antenna of a second radio unit; amplifying the first 60 GHz RF signal, and converting the first 60 GHz RF signal into a second upstream protection IF signal at a second transceiver of the second radio unit; converting the second upstream protection IF signal into a second upstream protection digital data at a second modulator/demodulator unit of the second radio unit; receiving the second upstream protection digital data at a second protection interface of the second radio unit. 
         [0024]    In a further embodiment, provided is a method implementing an all outdoor radios protection system using a wireless channel operating at a license-free 60 GHz band, the method further including the steps of receiving a second downstream protection digital signal at the second protection interface; converting the second downstream protection digital signal into a second downstream protection intermediate frequency (IF) signal at the second modulator/demodulator unit; converting the second downstream protection IF signal into a second 60 GHz radio frequency (RF) signal, and amplifying the second 60 GHz RF signal at the second transceiver; transmitting the second 60 GHz RF signal at the second antenna; receiving the second 60 GHz RF signal at the first antenna; amplifying the second 60 GHz RF signal, and converting the second 60 GHz RF signal into a first upstream protection IF signal at the first transceiver; converting the first upstream protection IF signal into a first upstream protection digital data at the first modulator/demodulator unit; receiving the first upstream protection digital data at a first protection interface of the second radio unit. 
         [0025]    In yet another embodiment, the first antenna and the second antenna are configured to operate at the license-free 60 GHz band. 
         [0026]    In yet another embodiment, the first radio unit and the second radio unit are configured to operate at a space diversity manner. 
         [0027]    In yet another embodiment, the first radio unit and the second radio unit are configured to operate at a frequency diversity manner. 
         [0028]    In yet another embodiment, the first radio unit and the second radio unit are configured to operate at a hybrid diversity manner. 
         [0029]    In yet a further embodiment, an all outdoor radios protection system is provided using a wireless channel operating at a license-free 60 GHz band including a first radio unit, where the first radio unit includes a first protection interface configured to receive a first downstream protection digital data; a first modulator/demodulator unit configured to convert the first downstream protection digital signal into a first downstream protection intermediate frequency (IF) signal; and a first transceiver configured to convert the first downstream protection IF signal into a first 60 GHz radio frequency (RF) signal, and amplify the first 60 GHz RF signal; a first antenna configured to transmit the first 60 GHz RF signal; a second radio unit, where the second radio unit includes a second antenna configured to receive the first 60 GHz RF signal; a second transceiver configured to amplify the first 60 GHz RF signal, and convert the first 60 GHz RF signal into a second upstream protection IF signal; a second modulator/demodulator unit configured to convert the second upstream protection IF signal into a second upstream protection digital data; a second protection interface configured to receive the second upstream protection digital data. 
         [0030]    In yet another embodiment, an all outdoor radios protection system is provided using a wireless channel operating at a license-free 60 GHz band, wherein the second protection interface is further configured to receive a second downstream protection digital data; the second modulator/demodulator unit is further configured to convert the second downstream protection digital data into a second downstream protection IF signal; the second transceiver is further configured to convert the second downstream protection IF signal into a second 60 GHz RF signal, and amplify the second 60 GHz RF signal; the second antenna is further configured to transmit the second 60 GHz RF signal; the first antenna is further configured to receive the second 60 GHz RF signal; the first transceiver is further configured to amplify the second 60 GHz RF signal, and convert the second 60 GHz RF signal into a first upstream protection IF signal; the first modulator/demodulator unit is further configured to convert the first upstream protection IF signal into a first upstream protection digital data; the first protection interface is further configured to receive the first upstream protection digital data. 
         [0031]    In accordance with some embodiments of the present invention, a system and method for implementing an XPIC application for an all outdoor radios system uses a wireless channel operating at a license-free 60 GHz band that substantially obviates one or more problems due to the limitations and disadvantages of the related art. 
         [0032]    A wireless connection operating at the license-free 60 GHz band may be used to support both XPIC application and protection system for all outdoor radios to achieve a transmission speed of up to 10 Gbps in a full duplex mode, and therefore, to accommodate the bandwidth needs for current microwave radio applications, and for future capacity growth. In particular, the replacement of the conventional wired connection in both XPIC application and protection system with the license-free 60 GHz wireless connection eliminates multiple outdoor cables between radio units and multiple weatherproof connectors for cables on all outdoor radio units. For example, only one connector of a 60 GHz antenna is required for each outdoor radio unit. Further, the signal links for both XPIC application and protection system can be consolidated into a common 60 GHz wireless connection. Therefore, the installation of the all outdoor radio units is simplified and the associated maintenance cost is reduced. 
         [0033]    In an embodiment, a method is provided for implementing an all outdoor radios XPIC application using a wireless channel operating at a license-free 60 GHz band, the method comprising the steps of: receiving a first downstream XPIC IF signal at a first receiver of a first radio unit; transmitting the first downstream XPIC IF signal to a first demodulator of the first radio unit and a first transceiver of the first radio unit, respectively; converting the first downstream XPIC IF signal into a first 60 GHz RF signal, and amplifying the first 60 GHz RF signal at the first transceiver of the first radio unit; transmitting the first 60 GHz RF signal at a first 60 GHz antenna of the first radio unit; receiving the first 60 GHz RF signal at a second 60 GHz antenna of a second radio unit; amplifying the first 60 GHz RF signal, and converting the first 60 GHz RF signal into a second upstream XPIC IF signal at a second transceiver of the second radio unit; and transmitting the second upstream XPIC IF signal to a second demodulator of the second radio unit. 
         [0034]    In a further embodiment, a method is provided for implementing an all outdoor radios XPIC application using a wireless channel operating at a license-free 60 GHz band of claim  1 , the method further comprising the steps of: receiving a second downstream XPIC IF signal at a second receiver of the second radio unit; transmitting the second downstream XPIC IF signal to the second demodulator of the second radio unit and the second transceiver of the second radio unit, respectively; converting the second downstream XPIC IF signal into a second 60 GHz RF signal, and amplifying the second 60 GHz RF signal at the second transceiver of the second radio unit; transmitting the second 60 GHz RF signal at the second 60 GHz antenna of the second radio unit; receiving the second 60 GHz RF signal at the first 60 GHz antenna of the first radio unit; amplifying the second 60 GHz RF signal, and converting the second 60 GHz RF signal into a first upstream XPIC IF signal at the first transceiver of the first radio unit; and transmitting the first upstream XPIC IF signal to the first demodulator of the first radio unit. 
         [0035]    In yet another embodiment, the first radio unit is configured to use vertical polarization of an antenna coupling unit (ACU), and the second radio unit is configured to use horizontal polarization of the antenna coupling unit, both the first and second radio units being coupled to the antenna coupling unit. 
         [0036]    In yet another embodiment, the first demodulator is configured to cancel interference of the horizontal polarization in the first downstream XPIC IF signal using the first upstream XPIC IF signal at the first demodulator of the first radio unit. 
         [0037]    In yet another embodiment, the second demodulator is configured to cancel interference of the vertical polarization in the second downstream XPIC IF signal using the second upstream XPIC IF signal at the second demodulator of the second radio unit. 
         [0038]    In yet another embodiment, the first downstream XPIC IF signal and the second downstream XPIC IF signal are configured to use different carrier frequencies within the license-free 60 GHz band. 
         [0039]    In yet a further embodiment, an all outdoor radios system is configured with an XPIC application using a wireless channel operating at a license-free 60 GHz band, the system comprising: an antenna coupling unit; a first radio unit further comprising: a first receiver configured to receive a first downstream XPIC IF signal from a first duplexer; a first demodulator configured to receive the first downstream XPIC IF signal and a first upstream XPIC IF signal, respectively; a first transceiver configured to convert the first downstream XPIC IF signal into a first 60 GHz RF signal, and amplify the first 60 GHz RF signal; and a first 60 GHz antenna configured to transmit the first 60 GHz RF signal; a second radio unit further comprising: a second 60 GHz antenna configured to receive the first 60 GHz RF signal; a second transceiver configured to amplify the first 60 GHz RF signal, and convert the first 60 GHz RF signal into a second upstream XPIC IF signal; a second demodulator configured to receive the second upstream XPIC IF signal and a second downstream XPIC IF signal, respectively; and a second receiver configured to receive the second downstream XPIC IF signal from a second duplexer; wherein the first radio unit and the second radio unit are, respectively, coupled to the antenna coupling unit. 
         [0040]    In yet another embodiment, the second transceiver is further configured to convert the second downstream XPIC IF signal into a second 60 GHz RF signal, and amplify the second 60 GHz RF signal; the second 60 GHz antenna is further configured to transmit the second 60 GHz RF signal; the first 60 GHz antenna is further configured to receive the second 60 GHz RF signal; and the first transceiver is further configured to amplify the second 60 GHz RF signal, and convert the second 60 GHz RF signal into the first upstream XPIC IF signal. 
         [0041]    In yet another embodiment, the first demodulator of the first radio unit is further configured to cancel interference of the horizontal polarization in the first downstream XPIC IF signal using the first upstream XPIC IF signal. 
         [0042]    In yet another embodiment, the second demodulator of the second radio unit is further configured to cancel interference of the vertical polarization in the second downstream XPIC IF signal using the second upstream XPIC IF signal. 
         [0043]    In yet another embodiment, the first downstream XPIC IF signal and the second downstream XPIC IF signal are configured to use different carrier frequencies within the license-free 60 GHz band. 
         [0044]    In yet another embodiment, a method is provided for implementing an all outdoor radios protection system and an all outdoor radios XPIC application using a wireless connection operating at a license-free 60 GHz band, the method comprising the steps of: receiving a first downstream XPIC IF signal at a first IF combiner of a first radio unit; receiving a first downstream protection IF signal at the first IF combiner of the first radio unit; combining the first downstream XPIC IF signal and the first downstream protection IF signal, and generating a first downstream combined IF signal at the first IF combiner of the first radio unit; converting the first downstream combined IF signal into a first 60 GHz RF signal, and amplifying the first 60 GHz RF signal at a first transceiver of the first radio unit; transmitting the first 60 GHz RF signal at a first 60 GHz antenna of the first radio unit; receiving the first 60 GHz RF signal at a second 60 GHz antenna of a second radio unit; amplifying the first 60 GHz RF signal, and converting the first 60 GHz RF signal into a second upstream combined IF signal at a second transceiver of the second radio unit; extracting a second upstream XPIC IF signal from the second upstream combined IF signal at a second IF splitter of the second radio unit; transmitting the second upstream XPIC IF signal to a second demodulator of the second radio unit; receiving the first 60 GHz RF signal at a third 60 GHz antenna of a third radio unit; amplifying the first 60 GHz RF signal, and converting the first 60 GHz RF signal into a third upstream combined IF signal at a third transceiver of the third radio unit; extracting a third upstream protection IF signal from the third upstream combined IF signal at a third IF splitter of the third radio unit, which further includes the steps of converting the third upstream protection IF signal into a third upstream protection digital packet at a third modem of the third radio unit; decapsulating the third upstream protection digital packet, and converting the third upstream protection digital packet into a third upstream protection digital signal; and transmitting the third upstream protection digital signal to a third protection interface of the third radio unit. 
         [0045]    In a further embodiment, the first downstream protection IF signal is generated by: receiving a first downstream protection digital signal at a first protection interface of the first radio unit, encapsulating the first downstream protection digital signal into a first downstream protection digital packet at a first wireless controller of the first radio unit, and converting the first downstream protection digital packet into the first downstream protection IF signal at a first modem of the first radio unit 
         [0046]    In yet another embodiment, a method is provided for implementing an all outdoor radios protection system and an all outdoor radios XPIC application using a wireless connection operating at a license-free 60 GHz band, the method further comprising the steps of: receiving a second downstream XPIC IF signal at a second IF combiner of the second radio unit; receiving a second downstream protection IF signal at the second IF combiner of the second radio unit; combining the second downstream XPIC IF signal and the second downstream protection IF signal, and generating a second downstream combined IF signal at a second IF combiner of the second radio unit; converting the second downstream combined IF signal into a second 60 GHz RF signal, and amplifying the second 60 GHz RF signal at the second transceiver of the second radio unit; transmitting the second 60 GHz RF signal at the second antenna of the second radio unit; receiving the second 60 GHz RF signal at the first antenna of the first radio unit; amplifying the second 60 GHz RF signal, and converting the second 60 GHz RF signal into a first upstream combined IF signal at the first transceiver of the first radio unit; extracting a first upstream XPIC IF signal from the first upstream combined IF signal at a first IF splitter of the first radio unit; transmitting the first upstream XPIC IF signal to a first demodulator of the first radio unit; receiving the second 60 GHz RF signal at a fourth antenna of a fourth radio unit, amplifying the second 60 GHz RF signal, and converting the second 60 GHz RF signal into a fourth upstream combined IF signal at a fourth transceiver of the fourth radio unit; extracting a fourth upstream protection IF signal from the fourth upstream combined IF signal at a fourth IF splitter of the fourth radio unit, which further includes the steps of converting the fourth upstream protection IF signal into a fourth upstream protection digital packet at a fourth modem of the fourth radio unit; decapsulating the fourth upstream protection digital packet, and converting the fourth upstream protection digital packet into a fourth upstream protection digital signal; transmitting the fourth upstream protection digital signal to a fourth upstream protection interface of the fourth radio unit. 
         [0047]    In a further embodiment, the second downstream protection IF signal is generated by: receiving a second downstream protection digital signal at a second protection interface of the second radio unit; encapsulating the second downstream protection digital signal into a second downstream protection digital packet at a second wireless controller of the second radio unit; and converting the second downstream protection digital packet into the second downstream protection IF signal at a second modem of the second radio unit. 
         [0048]    In yet another embodiment, a method is provided for implementing an all outdoor radios protection system and an all outdoor radios XPIC application using a wireless connection operating at a license-free 60 GHz band, the method further comprising the steps of: receiving a third downstream XPIC IF signal at a third IF combiner of the third radio unit; receiving a third downstream protection IF signal at the third IF combiner of the third radio unit; combining the third downstream XPIC IF signal and the third downstream protection IF signal, and generating a third downstream combined IF signal at the third IF combiner of the third radio unit; converting the third downstream combined IF signal into a third 60 GHz RF signal, and amplifying the third 60 GHz RF signal at the third transceiver of the third radio unit; transmitting the third 60 GHz RF signal at the third antenna of the third radio unit; receiving the third 60 GHz RF signal at the fourth antenna of the fourth radio unit; amplifying the third 60 GHz RF signal, and converting the third 60 GHz RF signal into a fourth upstream combined IF signal at the fourth transceiver of the fourth radio unit; extracting a fourth upstream XPIC IF signal from the fourth upstream combined IF signal at the fourth IF splitter of the fourth radio unit; transmitting the fourth upstream XPIC IF signal to a fourth demodulator of the fourth radio unit; receiving the third 60 GHz RF signal at the first antenna of the first radio unit; amplifying the third 60 GHz RF signal, and converting the third 60 GHz RF signal into the first upstream combined IF signal at the first transceiver of the first radio unit; extracting a first upstream protection IF signal from the first upstream combined IF signal at the first IF splitter of the first radio unit, which further includes the steps of converting the first upstream protection IF signal into a first upstream protection digital packet at a first modem of the first radio unit; decapsulating the first upstream protection digital packet, and converting the first upstream protection digital packet into a first upstream protection digital signal; and transmitting the first upstream protection digital signal to a first protection interface of the first radio unit. 
         [0049]    In a further embodiment, the third downstream protection IF signal is generated by: receiving a third downstream protection digital signal at a third protection interface of the third radio unit; encapsulating the third downstream protection digital signal into a third downstream protection digital packet at a third wireless controller of the third radio unit; and converting the third downstream protection digital packet into the third downstream protection IF signal at a third modem of the third radio unit. 
         [0050]    In yet another embodiment, a method is provided for implementing an all outdoor radios protection system and an all outdoor radios XPIC application using a wireless connection operating at a license-free 60 GHz band, the method further comprising the steps of: receiving a fourth downstream XPIC IF signal at a fourth IF combiner of the fourth radio unit; receiving a fourth downstream protection IF signal at the fourth IF combiner of the fourth radio unit; combining the fourth downstream XPIC IF signal and the fourth downstream protection IF signal, and generating a fourth downstream combined IF signal at a fourth IF combiner of the fourth radio unit; converting the fourth downstream combined IF signal into a fourth 60 GHz RF signal, and amplifying the fourth 60 GHz RF signal at the fourth transceiver of the fourth radio unit; transmitting the fourth 60 GHz RF signal at the fourth antenna of the fourth radio unit; receiving the fourth 60 GHz RF signal at the third antenna of the third radio unit; amplifying the fourth 60 GHz RF signal, and converting the fourth 60 GHz RF signal into the third upstream combined IF signal at the third transceiver of the third radio unit; extracting a third upstream XPIC IF signal from the third upstream combined IF signal at the third IF splitter of the third radio unit; transmitting the third upstream XPIC IF signal to a third demodulator of the third radio unit; receiving the fourth 60 GHz RF signal at the second antenna of the second radio unit; amplifying the fourth 60 GHz RF signal, and converting the fourth 60 GHz RF signal into the second upstream combined IF signal at the second transceiver of the second radio unit; extracting the second upstream protection IF signal from the second upstream combined IF signal at the second IF splitter of the second radio unit, which further includes the steps of converting the second upstream protection IF signal into a second upstream protection digital packet at a second modem of the second radio unit; decapsulating the second upstream protection digital packet, and converting the second upstream protection digital packet into a second upstream protection digital signal; and transmitting the second upstream protection digital signal to a second protection interface of the second radio unit. 
         [0051]    In a further embodiment, the fourth downstream protection IF signal is generated by: receiving a fourth downstream protection digital signal at a fourth protection interface of the fourth radio unit; encapsulating the fourth downstream protection digital signal into a fourth downstream protection digital packet at a fourth wireless controller of the fourth radio unit; and converting the fourth downstream protection digital packet into the fourth downstream protection IF signal at a fourth modem of the fourth radio unit. 
         [0052]    In yet another embodiment, the first radio unit and the third radio unit are configured to use vertical polarization, and operate as a vertical polarization protection pair, and the second radio unit and the fourth radio unit are configured to use horizontal polarization, and operate as a horizontal polarization protection pair. 
         [0053]    In yet another embodiment, the first radio unit and the second radio unit are configured to operate as a first XPIC pair, and the third radio unit and the fourth radio unit configured to operate as a second XPIC pair. 
         [0054]    In yet another embodiment, the method of implementing an all outdoor radios protection system and an all outdoor radios XPIC application using a wireless connection operating at a license-free 60 GHz band further comprises the step of cancelling interference of the horizontal polarization in the first downstream XPIC IF signal using the first upstream XPIC IF signal at the first demodulator of the first radio unit. 
         [0055]    In yet another embodiment, the method of implementing an all outdoor radios protection system and an all outdoor radios XPIC application using a wireless connection operating at a license-free 60 GHz band further comprises the step of cancelling interference of the vertical polarization in the second downstream XPIC IF signal using the second upstream XPIC IF signal at the second demodulator of the second radio unit. 
         [0056]    In yet another embodiment, the first downstream XPIC IF signal and the second downstream XPIC IF signal are configured to use different carrier frequencies within the license-free 60 GHz band. 
         [0057]    In yet another embodiment, the method of implementing an all outdoor radios protection system and an all outdoor radios XPIC application using a wireless connection operating at a license-free 60 GHz band further comprises the step of cancelling interference of the horizontal polarization in the third downstream XPIC IF signal using the third upstream XPIC IF signal at the third demodulator of the third radio unit. 
         [0058]    In yet another embodiment, the method of implementing an all outdoor radios protection system and an all outdoor radios XPIC application using a wireless connection operating at a license-free 60 GHz band further comprises the step of cancelling interference of the vertical polarization in the fourth downstream XPIC IF signal using the fourth upstream XPIC IF signal at the fourth demodulator of the fourth radio unit. 
         [0059]    In yet another embodiment, a protection interconnection within any one of the vertical polarization protection pair and the horizontal polarization protection pair and an XPIC interconnection within any one of the first XPIC pair and the second XPIC pair are configured to use different channels allocated within the license-free 60 GHz band. 
         [0060]    In yet a further embodiment, an all outdoor radios system is configured with a protection system and an XPIC application using a wireless connection operating at a license-free 60 GHz band, the system further comprising a first XPIC pair including: a first antenna coupling unit; a first radio unit configured to use vertical polarization of the first antenna coupling unit and a second radio unit configured to use horizontal polarization of the first antenna coupling unit, wherein the first radio unit and the second radio unit are, respectively, coupled to the first antenna coupling unit; a second XPIC pair including: a second antenna coupling unit; a third radio unit configured to use vertical polarization of the second antenna coupling unit; and a fourth radio unit configured to use horizontal polarization of the second antenna coupling unit of the second antenna coupling unit, wherein the third radio unit and the fourth radio unit are connected to the second antenna coupling unit; wherein each of the first radio unit, the second radio unit, the third radio unit, and the fourth radio unit includes: a duplexer; a receiver configured to receive a downstream XPIC IF signal from the duplexer; a demodulator configured to receive the downstream XPIC IF signal and an upstream XPIC IF signal, and cancel interference of an opposite polarization in the downstream XPIC IF signal using the upstream XPIC IF signal; a protection interface configured to receive a downstream protection digital signal; a wireless controller configured to encapsulate the downstream protection digital signal into a downstream protection digital packet addressed to a destination radio unit; a modem configured to convert the downstream protection digital packet into a downstream protection IF signal; an IF combiner configured to combine the downstream XPIC IF signal and the downstream protection IF signal, and generate a downstream combined IF signal; an IF splitter configured to receive an upstream combined IF signal, and extract the upstream XPIC IF signal and the upstream protection IF signal from the upstream combined IF signal, respectively; a transceiver configured to convert the downstream combined IF signal into a downstream 60 GHz RF signal, and amplify the downstream 60 GHz RF signal; and a 60 GHz antenna configured to transmit the downstream 60 GHz RF signal. 
         [0061]    In yet another embodiment, the 60 GHz antenna is further configured to receive an upstream 60 GHz RF signal; the transceiver is further configured to amplify the upstream 60 GHz RF signal, and convert the upstream 60 GHz RF signal into the upstream combined IF signal; the modem is further configured to convert the upstream protection IF signal into the upstream protection digital packet; the wireless controller is further configured to decapsulate the upstream protection digital packets, accept the upstream protection digital packet addressed to the destination radio unit that includes the wireless controller, and convert the accepted upstream protection digital packet into the upstream protection digital signal; and the protection interface is further configured to receive the upstream protection digital signal. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0062]    The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated herein and constitute a part of the specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings: 
           [0063]      FIG. 1A  is an exemplary illustration of an all outdoor radios link aggregation system with a star-like wired connection in related art; 
           [0064]      FIG. 1B  is another exemplary illustration of an all outdoor radios link aggregation system with a daisy-chain wired connection in related art; 
           [0065]      FIG. 1C  illustrates an exemplary illustration of an all outdoor radios protection system using a wired connection in related art; 
           [0066]      FIG. 1D  is an exemplary illustration of an all outdoor radios system implemented with an XPIC application using a wired connection in related art; 
           [0067]      FIG. 1E  is an exemplary illustration of an all outdoor radios system implemented with a protection system and an XPIC application using a wired connection in related art; 
           [0068]      FIG. 2  illustrates an exemplary embodiment of an all outdoor radios link aggregation system using a wireless channel operating at a license-free 60 GHz band in accordance with the present invention; 
           [0069]      FIG. 3  illustrates another exemplary embodiment of an all outdoor radios link aggregation system using a wireless channel operating at a license-free 60 GHz band in accordance with the present invention; 
           [0070]      FIG. 4  illustrates an exemplary method performed by an all outdoor radios link aggregation system using a wireless channel operating at a license-free 60 GHz band in accordance with the present invention; 
           [0071]      FIG. 5  illustrates another exemplary method performed by an all outdoor radios link aggregation system using a wireless channel operating at a license-free 60 GHz band in accordance with the present invention; 
           [0072]      FIG. 6  illustrates an exemplary embodiment of an all outdoor radios protection system using a wireless channel operating at a license-free 60 GHz band in accordance with some embodiments of the present invention; 
           [0073]      FIG. 7  illustrates another exemplary embodiment of an all outdoor radios protection system using a wireless channel operating at a license-free 60 GHz band in accordance with some embodiments of the present invention; 
           [0074]      FIG. 8  illustrates an exemplary method of an all outdoor radios protection system using a wireless channel operating at a license-free 60 GHz band in accordance with some embodiments of the present invention; 
           [0075]      FIG. 9  illustrates another exemplary method of an all outdoor radios protection system using a wireless channel operating at a license-free 60 GHz band in accordance with some embodiments of the present invention; 
           [0076]      FIG. 10  illustrates an exemplary embodiment of an all outdoor radios system configured with an XPIC application using a wireless channel operating at a license-free 60 GHz band in accordance with the present invention; 
           [0077]      FIG. 11  illustrates another exemplary embodiment of an all outdoor radios system configured with an XPIC application using a wireless channel operating at a license-free 60 GHz band in accordance with the present invention; 
           [0078]      FIG. 12  illustrates an exemplary embodiment of an all outdoor radios system configured with a protection system and an XPIC application using a wireless channel operating at a license-free 60 GHz band in accordance with the present invention; 
           [0079]      FIG. 13  illustrates another exemplary embodiment of an all outdoor radios system configured with a protection system and an XPIC application using a wireless channel operating at a license-free 60 GHz band in accordance with the present invention; 
           [0080]      FIG. 14  illustrates yet another exemplary embodiment of an all outdoor radios system configured with a protection system and an XPIC application using a wireless channel operating at a license-free 60 GHz band in accordance with the present invention; 
           [0081]      FIG. 15  illustrates yet another exemplary embodiment of an all outdoor radios system configured with a protection system and an XPIC application using a wireless channel operating at a license-free 60 GHz band in accordance with the present invention; 
           [0082]      FIG. 16  illustrates an exemplary method performed by an all outdoor radios system configured with an XPIC application using a wireless channel operating at a license-free 60 GHz band in accordance with the present invention; 
           [0083]      FIG. 17  illustrates another exemplary method performed by an all outdoor radios system configured with an XPIC application using a wireless channel operating at a license-free 60 GHz band in accordance with the present invention; 
           [0084]      FIG. 18  illustrates an exemplary method performed by an all outdoor radios system configured with a protection system and an XPIC application using a wireless channel operating at a license-free 60 GHz band in accordance with the present invention; 
           [0085]      FIG. 19  illustrates another exemplary method performed by an all outdoor radios system configured with a protection system and an XPIC application using a wireless channel operating at a license-free 60 GHz band in accordance with the present invention; 
           [0086]      FIG. 20  illustrates yet another exemplary method performed by an all outdoor radios system configured with a protection system and an XPIC application using a wireless channel operating at a license-free 60 GHz band in accordance with the present invention; and 
           [0087]      FIG. 21  illustrates yet another exemplary method performed by an all outdoor radios system configured with a protection system and an XPIC application using a wireless channel operating at a license-free 60 GHz band in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0088]    Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings. In the following detailed description, numerous non-limiting specific details are set forth in order to assist in understanding the subject matter presented herein. It will be apparent, however, to one of ordinary skill in the art that various alternatives may be used without departing from the scope of the present invention and the subject matter may be practiced without these specific details. For example, it will be apparent to one of ordinary skill in the art that the subject matter presented herein can be implemented on any type of all outdoor radios link aggregation system using a wireless channel. 
         [0089]      FIG. 2  illustrates an exemplary embodiment of an all outdoor radios link aggregation system using a wireless channel operating at a license-free 60 GHz band in accordance with the present invention. In the exemplary embodiment  300 A, the all outdoor radios link aggregation system may include a first radio unit  301 A and at least a second radio unit  302 A. The first radio unit  301 A may include a first rear-end transceiver  304 A, a first rear-end modem  305 A, a first digital data interface  306 A, a first wireless controller  307 A, a first front-end modem  308 A, a first front-end transceiver  309 A, and a first 60 GHz antenna  310 A. The second radio unit  302 A may include a second rear-end transceiver  311 A, a second rear-end modem  312 A, a second digital data interface  313 A, a second wireless controller  314 A, a second front-end modem  315 A, a second front-end transceiver  316 A, a second 60 GHz antenna  317 A. An upstream user data  318 A may be received at the first digital data interface  306 A. The first digital data interface  306 A may split the upstream user data  318 A into at least a first sub-stream digital data  319 A and a second sub-stream digital data  320 A. The first sub-stream digital data  319 A may be transmitted through the first rear-end modem  305 A and the first rear-end transceiver  304 A. The second sub-stream digital data  320 A may be transmitted to the first wireless controller  307 A. The first wireless controller  307 A may encapsulate the second sub-stream digital data  320 A into a second sub-stream data packet  321 A addressed to a first destination radio unit. The first front-end modem  308 A may convert the second sub-stream data packet  321 A into a first downstream data intermediate frequency (IF) signal  322 A. The first front-end transceiver  309 A may convert the first downstream data IF signal  322 A into a first 60 GHz radio frequency (RF) signal  323 A, and amplify the first 60 GHz RF signal  323 A. The first 60 GHz antenna  310 A may transmit the first 60 GHz RF signal  323 A. The second 60 GHz antenna  317 A may receive the first 60 GHz RF signal  323 A. 
         [0090]    The second front-end transceiver  316 A in the second radio unit  302 A may amplify the first 60 GHz RF signal  323 A, and convert the first 60 GHz RF signal  323 A into a second upstream data IF signal  324 A. The second front-end modem  315 A may convert the second upstream data IF signal  324 A into a second upstream data packet  325 A. The second wireless controller  314 A may decapsulate the second upstream data packet  325 A, accept the second upstream data packet  325 A if the second radio unit  302 A is the addressed first destination radio unit, and convert the second upstream data packet  325 A into a second upstream digital data  326 A. The second digital data interface  313 A may receive the second upstream digital data  326 A, and transmit the second upstream digital data  326 A through the second rear-end modem  312 A and the second rear-end transceiver  311 A. 
         [0091]      FIG. 3  illustrates another exemplary embodiment of an all outdoor radios link aggregation system using a wireless channel operating at a license-free 60 GHz band in accordance with the present invention. In the exemplary embodiment  400 A, the all outdoor radios link aggregation system may include a first radio unit  401 A and at least a second radio unit  402 A. The first radio unit  401 A may include a first rear-end transceiver  404 A, a first rear-end modem  405 A, a first digital data interface  406 A, a first wireless controller  407 A, a first front-end modem  408 A, a first front-end transceiver  409 A, and a first 60 GHz antenna  410 A. The second radio unit  402 A may include a second rear-end transceiver  411 A, a second rear-end modem  412 A, a second digital data interface  413 A, a second wireless controller  414 A, a second front-end modem  415 A, a second front-end transceiver  416 A, and a second 60 GHz antenna  417 A. The first digital data interface  406 A may be further configured to receive a third sub-stream digital data  419 A. The second digital data interface  413 A in the second radio unit  402 A may be further configured to receive a fourth sub-stream digital data  427 A. The second wireless controller  414 A may be further configured to encapsulate the fourth sub-stream digital data  426 A from the second digital data interface  413 A into a fourth sub-stream data packet  425 A addressed to a second destination radio unit. The second front-end modem  415 A may be further configured to convert the fourth sub-stream data packet  425 A into a second downstream data IF signal  424 A. The second front-end transceiver  416 A may be further configured to convert the second downstream data IF signal  424 A into a second 60 GHz radio RF signal  423 A, and amplify the second 60 GHz RF signal  423 A. The second 60 GHz antenna  417 A may be further configured to transmit the second 60 GHz RF signal  423 A. The first 60 GHz antenna  410 A may be further configured to receive the second 60 GHz RF signal  423 A. The first front-end transceiver  409 A may be further configured to amplify the second 60 GHz RF signal  423 A, and convert the second 60 GHz RF signal  423 A into a first upstream data IF signal  422 A. The first front-end modem  408 A may be further configured to convert the first upstream data IF signal  422 A into a first upstream data packet  421 A. The first wireless controller  407 A may be further configured to decapsulate the first upstream data packet  421 A, accept the first upstream data packet  421 A if the first radio unit  401 A is the addressed second destination radio unit, and convert the first upstream data packet  421 A into a first upstream digital data  420 A. The first digital data interface  406 A may be further configured to receive the first upstream digital data  420 A, aggregate the first upstream digital data  420 A and the third sub-stream digital data  419 A, reconstruct a first downstream user data  418 A, and transmit the first downstream user data  418 A. 
         [0092]    In some embodiment, the first sub-stream digital data is configured with a data rate equal to or less than the throughput of the first radio unit and the second sub-stream digital data is configured with a data rate equal to or less than the throughput of the second radio unit. 
         [0093]    In some embodiment, the third sub-stream digital data is configured with a data rate equal to or less than the throughput of the first radio unit and the fourth sub-stream digital data is configured with a data rate equal to or less than the throughput of the second radio unit. 
         [0094]    In some embodiment, the first radio unit and the second radio unit are configured to connect to an ACU  304 A or  404 A. 
         [0095]      FIG. 4  illustrates an exemplary method of an all outdoor radios link aggregation system using a wireless channel operating at a license-free 60 GHz band in accordance with the present invention. The method includes: step  501 A for receiving an upstream user data at a first digital data interface of a first radio unit; step  502 A for splitting the upstream user data into at least a first sub-stream digital data and a second sub-stream digital data at the first digital data interface; step  503 A for transmitting the first sub-stream digital data through a first rear-end modem and a first rear-end transceiver of the first radio unit; step  504 A for transmitting the second sub-stream digital data to a first wireless controller of the first radio unit; step  505 A for encapsulating the second sub-stream digital data into a second sub-stream data packet addressed to a first destination radio unit at the first wireless controller, and transmitting the second sub-stream data packet to a first front-end modem of the first radio unit; step  506 A for converting the second sub-stream data packet into a first downstream data intermediate frequency (IF) signal at the first front-end modem, and transmitting the first downstream data IF signal to a first front-end transceiver of the first radio unit; step  507 A for converting the first downstream data IF signal into a first 60 GHz radio frequency (RF) signal, and amplifying the first 60 GHz RF signal at the first front-end transceiver; step  508 A for transmitting the first 60 GHz RF signal at a first 60 GHz antenna of the first radio unit; step  509 A for receiving the first 60 GHz RF signal at a second 60 GHz antenna of a second radio unit; step  510 A for amplifying the first 60 GHz RF signal, and converting the first 60 GHz RF signal into a second upstream data IF signal at a second front-end transceiver of the second radio unit, and transmitting the second upstream data IF signal to a second front-end modem of the second radio unit; step  511 A for converting the second upstream data IF signal into a second upstream data packet, and transmitting the second upstream data packet to a second wireless controller of the second radio unit; step  512 A for decapsulating the second upstream data packet at the second wireless controller, accepting the second upstream data packet if the second radio unit is the addressed first destination radio unit, and converting the second upstream data packet into a second upstream digital data; step  513 A for transmitting the second upstream digital data to a second digital data interface of the second radio unit; and step  514 A for transmitting the second upstream digital data through a second rear-end modem and a second rear-end transceiver of the second radio unit. 
         [0096]      FIG. 5  illustrates another exemplary method of an all outdoor radios link aggregation system using a wireless channel operating at a license-free 60 GHz band in accordance with the present invention. The method includes: step  601 A for receiving at least a third sub-stream digital data at the first digital data interface and a fourth sub-stream digital data at the second digital data interface; step  602 A for transmitting the fourth sub-stream digital data to the second wireless controller; step  603 A for encapsulating the fourth sub-stream digital data into a fourth sub-stream data packet addressed to a second destination radio unit at the second wireless controller, and transmitting the fourth sub-stream data packet to the second front-end modem; step  604 A for converting the fourth sub-stream data packet into a second downstream data IF signal at the second front-end modem, and transmitting the second downstream data IF signal to the second front-end transceiver; step  605 A for converting the second downstream data IF signal into a second 60 GHz radio RF signal, and amplifying the second 60 GHz RF signal at the second front-end transceiver; step  606 A for transmitting the second 60 GHz RF signal at the second 60 GHz antenna; step  607 A for receiving the second 60 GHz RF signal at the first 60 GHz antenna; step  608 A for amplifying the second 60 GHz RF signal, and converting the second 60 GHz RF signal into a first upstream data IF signal at the first front-end transceiver, and transmitting the first upstream data IF signal to the first front-end modem; step  609 A for converting the first upstream data IF signal into a first upstream data packet, and transmitting the first upstream data packet to the first wireless controller; step  610 A for decapsulating the first upstream data packet, accepting the first upstream data packet if the first radio unit is the addressed second destination radio unit, and converting the first upstream data packet into a first upstream digital data; step  611 A for transmitting the first upstream digital data to the first digital data interface; and step  612 A for aggregating the first upstream digital data and the third sub-stream digital data, reconstructing a first downstream user data, and transmitting the first downstream user data. 
         [0097]      FIG. 6  illustrates an exemplary embodiment  200 B of an all outdoor radios protection system using a wireless channel operating at a license-free 60 GHz band in accordance with some embodiments of the present invention. In the exemplary embodiment  200 B, the all outdoor radios protection system may include a first radio unit  201 B and a second radio unit  202 B. The first radio unit  201 B may include a first protection interface  203 B, a first modulator/demodulator unit  204 B, a first transceiver  205 B, and a first antenna  206 B. The second radio unit  202 B may include a second protection interface  207 B, a second modulator/demodulator unit  208 B, a second transceiver  209 B, and a second antenna  210 B. A first downstream protection digital data  211 B may be received at the first protection interface  203 B, and transmitted to the first modulator/demodulator unit  204 B. The first modulator/demodulator unit  204 B may convert the first downstream protection digital data  211 B into a first downstream protection intermediate frequency (IF) signal  212 B, and transmit the first downstream protection IF signal  212 B to the first transceiver  205 B. The first transceiver  205 B may convert the first downstream protection IF signal  212 B into a first 60 GHz radio frequency (RF) signal  213 B, and amplifies the first 60 GHz RF signal  213 B. The amplified first 60 GHz RF signal  213 B may be transmitted to a first antenna  206 B connected to the first transceiver  205 B. 
         [0098]    In some embodiment, the first antenna  206 B may transmit the first 60 GHz RF signal  213 B to the second antenna  210 B. The second antenna  210 B may transmit the received first 60 GHz RF signal  213 B to the second transceiver  209 B. The second transceiver  209 B may amplify the received first 60 GHz RF signal  213 B, and convert the received first 60 GHz RF signal  213 B into a second upstream protection IF signal  214 B. The second upstream protection IF signal  214 B may be transmitted to the second modulator/demodulator unit  208 B. The second modulator/demodulator unit  208 B may convert the second upstream protection IF signal  214 B into a second upstream protection digital data  215 B. The second upstream protection digital data  215 B may be received at the second protection interface  207 B. 
         [0099]    In some embodiment, the first antenna  206 B and the second antenna  210 B are configured to operate at the license-free 60 GHz band. 
         [0100]    In some embodiment, the first radio unit  201 B and the second radio unit  202 B are configured to operate at a space diversity manner. 
         [0101]    In another embodiment, the first radio unit  201 B and the second radio unit  202 B are configured to operate at a frequency diversity manner. 
         [0102]    In yet another embodiment, the first radio unit  201 B and the second radio unit  202 B are configured to operate at a hybrid diversity manner. 
         [0103]      FIG. 7  illustrates another exemplary embodiment  300 B of an all outdoor radios protection system using a wireless channel operating at a license-free 60 GHz band in accordance with some embodiments of the present invention. In the exemplary embodiment  300 B, the all outdoor radios protection system may include a first radio unit  301 B and a second radio unit  302 B. The first radio unit  301 B may include a first protection interface  303 B, a first modulator/demodulator unit  304 B, a first transceiver  305 B, and a first antenna  306 B. The second radio unit  302 B may include a second protection interface  307 B, a second modulator/demodulator unit  308 B, a second transceiver  309 B, and a second antenna  310 B. A second downstream protection digital data  31  lB may be received at the second protection interface  307 B, and transmitted to the second modulator/demodulator unit  308 B. The second modulator/demodulator unit  308 B may convert the second downstream protection digital data  311 B into a second downstream protection intermediate frequency (IF) signal  312 B, and transmit the second downstream protection IF signal  312 B to the second transceiver  309 B. The second transceiver  309 B may convert the second downstream protection IF signal  312 B into a second 60 GHz radio frequency (RF) signal  313 B, and amplifies the second 60 GHz RF signal  313 B. The amplified second 60 GHz RF signal  313 B may be transmitted to a second antenna  310 B connected to the second transceiver  309 B. 
         [0104]    In some embodiment, the second antenna  310 B may transmit the second 60 GHz RF signal  313 B to the first antenna  306 B. The first antenna  306 B may transmit the received second 60 GHz RF signal  313 B to the first transceiver  305 B. The first transceiver  305 B may amplify the received second 60 GHz RF signal  313 B, and convert the received second 60 GHz RF signal  313 B into a first upstream protection IF signal  315 B. The first upstream protection IF signal  314 B may be transmitted to the first modulator/demodulator unit  304 B. The first modulator/demodulator unit  304 B may convert the first upstream protection IF signal  314 B into a first upstream protection digital data  315 B. The first upstream protection digital data  315 B may be received at the first protection interface  303 B. 
         [0105]    In some embodiment, the first antenna  306 B and the second antenna  310 B are configured to operate at the license-free 60 GHz band. 
         [0106]    In some embodiment, the first radio unit  301 B and the second radio unit  302 B are configured to operate at a space diversity manner. 
         [0107]    In another embodiment, the first radio unit  301 B and the second radio unit  302 B are configured to operate at a frequency diversity manner. 
         [0108]    In yet another embodiment, the first radio unit  301 B and the second radio unit  302 B are configured to operate at a hybrid diversity manner. 
         [0109]      FIG. 8  illustrates an exemplary method of an all outdoor radios protection system using a wireless channel operating at a license-free 60 GHz band in accordance with some embodiments of the present invention. The method includes: step  401 B for receiving a first downstream protection digital signal  211 B at a first protection interface  203 B of a first radio unit  201 B, step  402 B for converting the first downstream protection digital signal  211 B into a first downstream protection intermediate frequency (IF) signal  212 B at a first modulator/demodulator unit  204 B of the first radio unit  201 B, step  403 B for converting the first downstream protection IF signal  212 B into a first 60 GHz radio frequency (RF) signal  213 B, and amplifying the first 60 GHz RF signal  213 B at a first transceiver  205 B of the first radio unit  201 B, step  404 B for transmitting the first 60 GHz RF signal  213 B at a first antenna  206 B of the first radio unit  201 B, step  405  for receiving the first 60 GHz RF signal  213 B at a second antenna  210 B of a second radio unit  202 B, step  406 B for amplifying the first 60 GHz RF signal  213 B, and converting the first 60 GHz RF signal  213 B into a second upstream protection IF signal  214 B at a second transceiver  209 B of the second radio unit  202 B, step  407 B for converting the second upstream protection IF signal  214 B into a second upstream protection digital data  215 B at a second modulator/demodulator unit  208 B of the second radio unit  202 B, step  408 B for receiving the second upstream protection digital data  215 B at a second protection interface  207 B of the second radio unit  202 B. 
         [0110]      FIG. 9  illustrates another exemplary method of an all outdoor radios protection system using a wireless channel operating at a license-free 60 GHz band in accordance with some embodiments of the present invention. The method includes: step  501 B for receiving a second downstream protection digital signal  311 B at the second protection interface  307 B, step  502 B for converting the second downstream protection digital signal  311 B into a second downstream protection intermediate frequency (IF) signal  312 B at the second modulator/demodulator unit  308 B, step  503 B for converting the second downstream protection IF signal  312 B into a second 60 GHz radio frequency (RF) signal  313 B, and amplifying the second 60 GHz RF signal  313 B at the second transceiver  309 B, step  504 B for transmitting the second 60 GHz RF signal  313 B at the second antenna  310 B, step  505 B for receiving the second 60 GHz RF signal  313 B at the first antenna  306 B, step  506 B for amplifying the second 60 GHz RF signal  313 B, and converting the second 60 GHz RF signal  313 B into a first upstream protection IF signal  314 B at the first transceiver  305 B, step  507 B for converting the first upstream protection IF signal  314 B into a first upstream protection digital data  315 B at the first modulator/demodulator unit  304 B, step  408 B for receiving the first upstream protection digital data  315 B at a first protection interface  303 B of the first radio unit  301 B. 
         [0111]      FIG. 10  illustrates an exemplary embodiment of an all outdoor radios system configured with an XPIC application using a wireless channel operating at a license-free 60 GHz band in accordance with the present invention. In the exemplary embodiment  300 C, the all outdoor radios system configured with an XPIC application using a wireless channel operating at a license-free 60 GHz band may include a first radio unit  301 C and a second radio unit  302 C, both of which are coupled to an ACU  350 C. The first radio unit  301 C may include a first duplexer  303 C, a first receiver  304 C, a first demodulator  305 C, a first transceiver  306 C, a first 60 GHz antenna  307 C, and a first digital data interface  308 C. The second radio unit  302 C may include a second duplexer  309 C, a second receiver  310 C, a second demodulator  311 C, a second transceiver  312 C, a second 60 GHz antenna  313 C, and a second digital data interface  314 C. A first downstream XPIC IF signal  315 C may be received at the first receiver  304 C, and transmitted to the first demodulator  305 C and the first transceiver  306 C, respectively. The first transceiver  306 C may convert the first downstream XPIC IF signal  315 C into a first 60 GHz RF signal  316 C, and amplify the first 60 GHz RF signal  316 C. The amplified first 60 GHz RF signal  316 C may be transmitted to a first 60 GHz antenna  307 C connected to the first transceiver  306 C. 
         [0112]    In some embodiment, the first 60 GHz antenna  307 C may transmit the first 60 GHz RF signal  316 C to the second 60 GHz antenna  313 C. The second 60 GHz antenna  313 C may transmit the received first 60 GHz RF signal  316 C to the second transceiver  312 C. The second transceiver  312 C may amplify the received first 60 GHz RF signal  316 C, and convert the received first 60 GHz RF signal  316 C into a second upstream XPIC IF signal  317 C. The second upstream XPIC IF signal  317 C may be transmitted to the second demodulator  311 C. 
         [0113]    In some embodiment, the first radio unit  301 C may use vertical polarization, and the second radio unit  302 C may use horizontal polarization. 
         [0114]    In some embodiment, the second demodulator  311 C may use the second upstream XPIC IF signal  317 C to cancel interference of the vertical polarization in the second downstream XPIC IF signal  318 C received at the second receiver  310 C. 
         [0115]      FIG. 11  illustrates another exemplary embodiment of an all outdoor radios system configured with an XPIC application using a wireless channel operating at a license-free 60 GHz band in accordance with the present invention. In the exemplary embodiment  400 C, the all outdoor radios system configured with an XPIC application using a wireless channel operating at a license-free 60 GHz band may include a first radio unit  401 C and a second radio unit  402 C, both of which are coupled to an ACU  450 C. The first radio unit  401 C may include a first duplexer  403 C, a first receiver  404 C, a first demodulator  405 C, a first transceiver  406 C, a first 60 GHz antenna  407 C, and a first digital data interface  408 C. The second radio unit  402 C may include a second duplexer  409 C, a second receiver  410 C, a second demodulator  411 C, a second transceiver  412 C, a second 60 GHz antenna  413 C, and a second digital data interface  414 C. A second downstream XPIC IF signal  415 C may be received at the second receiver  410 C, and transmitted to the second demodulator  411 C and the second transceiver  412 C, respectively. The second transceiver  412 C may convert the second downstream XPIC IF signal  415 C into a second 60 GHz RF signal  416 C, and amplify the second 60 GHz RF signal  416 C. The amplified second 60 GHz RF signal  416 C may be transmitted to a second 60 GHz antenna  413 C connected to the second transceiver  412 C. 
         [0116]    In some embodiment, the second 60 GHz antenna  413 C may transmit the second 60 GHz RF signal  416 C to the first 60 GHz antenna  407 C. The first 60 GHz antenna  407 C may transmit the received second 60 GHz RF signal  416 C to the first transceiver  406 C. The first transceiver  406 C may amplify the received second 60 GHz RF signal  416 C, and convert the received second 60 GHz RF signal  416 C into a first upstream XPIC IF signal  417 C. The first upstream XPIC IF signal  417 C may be transmitted to the first demodulator  405 C. 
         [0117]    In some embodiment, the first radio unit  401 C may use vertical polarization, and the second radio unit  402 C may use horizontal polarization. 
         [0118]    In some embodiment, the first demodulator  405 C may use the first upstream XPIC IF signal  417 C to cancel interference of the horizontal polarization in the first downstream XPIC IF signal  418 C received at the first receiver  404 C. 
         [0119]      FIG. 12  illustrates an exemplary embodiment of an all outdoor radios system configured with a protection system and an XPIC application using a wireless channel operating at a license-free 60 GHz band in accordance with the present invention. In the exemplary embodiment  500 C, the all outdoor radios system configured with a protection system and an XPIC application using a wireless channel operating at a license-free 60 GHz band may include: a first radio unit  501 C configured to use vertical polarization, a second radio unit  502 C configured to use horizontal polarization, a third radio unit  503 C configured to use vertical polarization, and a fourth radio unit  504 C configured to use horizontal polarization. The first radio unit  501 C and the second radio unit  502 C are communicatively coupled to an ACU  550 C and the third radio unit  503 C and the fourth radio unit  504 C are communicatively coupled to an ACU  555 C, respectively. The first radio unit  501 C may include a first duplexer  505 C, a first receiver  506 C, a first demodulator  507 C, a first protection interface  508 C, a first wireless controller  509 C, a first modem  510 C, a first IF combiner  511 C, a first IF splitter  512 C, a first transceiver  513 C, and a first 60 GHz antenna  514 C. A first downstream XPIC IF signal  515 C and a first downstream protection IF signal  516 C may be received at the first IF combiner  511 C. The first IF combiner  511 C may combine the first downstream XPIC IF signal  515 C and the first downstream protection IF signal  516 C, and generate a first downstream combined IF signal  519 C. The first downstream combined IF signal  519 C may be transmitted to the first transceiver  513 C. The first transceiver  513 C may convert the first downstream combined IF signal  519 C into a first 60 GHz RF signal  520 C, and amplify the first 60 GHz RF signal  520 C. The amplified first 60 GHz RF signal  520 C may be transmitted to a first 60 GHz antenna  514 C connected to the first transceiver  513 C. 
         [0120]    In some embodiment, a first downstream protection digital signal  517 C may be received at the first protection interface  508 C. The first downstream protection digital signal  517 C may be transmitted to the first wireless controller  509 C. The first wireless controller  509 C may encapsulate the first downstream protection digital signal  517 C into a first downstream protection digital packet  518 C, and transmit the first downstream protection digital packet  518 C to the first modem  510 C. The first modem  510 C may convert the first downstream protection digital packet  518 C into the first downstream protection IF signal  516 C, and transmit the first downstream protection IF signal  516 C to the first IF combiner  511 C. 
         [0121]    In some embodiment, the first 60 GHz RF signal  520 C may be received at a second 60 GHz antenna  521 C of the second radio unit  502 C. The second 60 GHz antenna  521 C may transmit the received first 60 GHz RF signal  520 C to a second transceiver  522 C of the second radio unit  502 C. The second transceiver  522 C may amplify the received first 60 GHz RF signal  520 C, and convert the received first 60 GHz RF signal  520 C into a second upstream combined IF signal  523 C. The second upstream combined IF signal  523 C may be transmitted to a second IF splitter  524 C of the second radio unit  502 C. The second IF splitter  524 C may extract a second upstream XPIC IF signal  525 C from the second upstream combined IF signal  523 C, and transmit the second upstream XPIC IF signal  525 C to a second demodulator  526 C of the second radio unit  502 C. The second demodulator  526 C may use the second upstream XPIC IF signal  525 C to cancel interference of the vertical polarization in the second downstream XPIC IF signal  537 C. 
         [0122]    In some embodiment, the first 60 GHz RF signal  520 C may be received at a third 60 GHz antenna  527 C of the third radio unit  503 C. The third 60 GHz antenna  527 C may transmit the received first 60 GHz RF signal  520 C to a third transceiver  528 C of the third radio unit  503 C. The third transceiver  528 C may amplify the received first 60 GHz RF signal  520 C, and convert the received first 60 GHz RF signal  520 C into a third upstream combined IF signal  529 C. The third upstream combined IF signal  529 C may be transmitted to a third IF splitter  530 C of the third radio unit  503 C. The third IF splitter  530 C may extract a third upstream protection IF signal  531 C from the third upstream combined IF signal  529 C. 
         [0123]    In some embodiment, the third upstream protection IF signal  531 C may be transmitted to a third modem  532 C of the third radio unit  503 C. The third modem  532 C may convert the third upstream protection IF signal  531 C into a third upstream protection digital packet  533 C, and transmit the third upstream protection digital packet  533 C to a third wireless controller  534 C of the third radio unit  503 C. The third wireless controller  534 C may decapsulate the third upstream protection digital packet  533 C, and convert the third upstream protection digital packet  533 C into a third upstream protection digital signal  535 C. The third upstream protection digital signal  535 C may be transmitted to a third protection interface  536 C of the third radio unit  503 C. 
         [0124]    In some embodiment, the first wireless controller  509 C of the first radio unit  501 C may encapsulate the first downstream protection digital signal  517 C into the first downstream protection digital packet  518 C addressed to a destination radio unit. The third wireless controller  534 C of the third radio unit  503 C may decapsulate the third upstream protection digital packet  533 C, accept only the upstream protection digital packet addressed to the destination radio unit that includes the third wireless controller  534 C, and convert the accepted upstream protection digital packet into the third upstream protection digital signal  535 C. 
         [0125]    In some embodiment, the first radio unit  501 C and the third radio unit  503 C may be configured to operate as a vertical polarization protection pair, and the second radio unit  502 C and the fourth radio unit  504 C may be configured to operate as a horizontal polarization protection pair. 
         [0126]    In some embodiment, the first radio unit  501 C and the second radio unit  502 C may be configured as a first XPIC pair, and the third radio unit  503 C and the fourth radio unit  504 C may be configured as a second XPIC pair. 
         [0127]    In some embodiment, the first downstream XPIC IF signal  515 C and the second downstream XPIC IF signal  537 C are configured to use different carrier frequencies within the license-free 60 GHz band. 
         [0128]    In some embodiment, a protection interconnection within any one of the vertical polarization protection pair and the horizontal polarization protection pair and an XPIC interconnection within any one of the first XPIC pair and the second XPIC pair are configured to use different channels allocated within the license-free 60 GHz band. 
         [0129]      FIG. 13  illustrates another exemplary embodiment of an all outdoor radios system configured with a protection system and an XPIC application using a wireless channel operating at a license-free 60 GHz band in accordance with the present invention. In the exemplary embodiment  600 C, the all outdoor radios system configured with a protection system and an XPIC application using a wireless channel operating at a license-free 60 GHz band may include: a first radio unit  601 C configured to use vertical polarization, a second radio unit  602 C configured to use horizontal polarization, a third radio unit  603 C configured to use vertical polarization, and a fourth radio unit  604 C configured to use horizontal polarization. The first radio unit  601 C and the second radio unit  602 C are communicatively coupled to an ACU  650 C and the third radio unit  603 C and the fourth radio unit  604 C are communicatively coupled to an ACU  655 C, respectively. The second radio unit  602 C may include a second duplexer  605 C, a second receiver  606 C, a second demodulator  607 C, a second protection interface  608 C, a second wireless controller  609 C, a second modem  610 C, a second IF combiner  611 C, a second IF splitter  612 C, a second transceiver  613 C, and a second 60 GHz antenna  614 C. A second downstream XPIC IF signal  615 C and a second downstream protection IF signal  616 C may be received at the second IF combiner  611 C. The second IF combiner  611 C may combine the second downstream XPIC IF signal  615 C and the second downstream protection IF signal  616 C, and generate a second downstream combined IF signal  619 C. The second downstream combined IF signal  619 C may be transmitted to the second transceiver  613 C. The second transceiver  613  may convert the second downstream combined IF signal  619 C into a second 60 GHz RF signal  620 C, and amplify the second 60 GHz RF signal  620 C. The amplified second 60 GHz RF signal  620 C may be transmitted to a second 60 GHz antenna  614 C connected to the second transceiver  613 C. 
         [0130]    In some embodiment, a second downstream protection digital signal  617 C may be received at the second protection interface  608 C. The second downstream protection digital signal  617 C may be transmitted to the second wireless controller  609 C. The second wireless controller  609 C may encapsulate the second downstream protection digital signal  617 C into a second downstream protection digital packet  618 C, and transmit the second downstream protection digital packet  618 C to the second modem  610 C. The second modem  610 C may convert the second downstream protection digital packet  618 C into the second downstream protection IF signal  616 C, and transmit the second downstream protection IF signal  616 C to the first IF combiner  611 C. 
         [0131]    In some embodiment, the second 60 GHz RF signal  620 C may be received at a first 60 GHz antenna  621 C of the first radio unit  601 C. The first 60 GHz antenna  621 C may transmit the received second 60 GHz RF signal  620 C to a first transceiver  622 C of the first radio unit  601 C. The first transceiver  622 C may amplify the received second 60 GHz RF signal  620 C, and convert the received second 60 GHz RF signal  620 C into a first upstream combined IF signal  623 C. The first upstream combined IF signal  623 C may be transmitted to a first IF splitter  624 C of the first radio unit  601 C. The first IF splitter  624 C may extract a first upstream XPIC IF signal  625 C from the first upstream combined IF signal  623 C, and transmit the first upstream XPIC IF signal  625 C to a first demodulator  626 C of the first radio unit  601 C. The first demodulator  626 C may use the first upstream XPIC IF signal  625 C to cancel interference of the horizontal polarization in the first downstream XPIC IF signal  637 C. 
         [0132]    In some embodiment, the second 60 GHz RF signal  620 C may be received at a fourth 60 GHz antenna  627 C of the fourth radio unit  604 C. The fourth 60 GHz antenna  627 C may transmit the received first 60 GHz RF signal  620 C to a fourth transceiver  628 C of the fourth radio unit  604 C. The fourth transceiver  628 C may amplify the received first 60 GHz RF signal  620 C, and convert the received first 60 GHz RF signal  620 C into a fourth upstream combined IF signal  629 C. The fourth upstream combined IF signal  629 C may be transmitted to a fourth IF splitter  630 C of the fourth radio unit  604 . The fourth IF splitter  630 C may extract a fourth upstream protection IF signal  631 C from the fourth upstream combined IF signal  629 C. 
         [0133]    In some embodiment, the fourth upstream protection IF signal  631 C may be transmitted to a fourth modem  632 C of the fourth radio unit  604 C. The fourth modem  632 C may convert the fourth upstream protection IF signal  631 C into a fourth upstream protection digital packet  633 C, and transmit the fourth upstream protection digital packet  633 C to a fourth wireless controller  634 C of the fourth radio unit  604 C. The fourth wireless controller  634 C may decapsulate the fourth upstream protection digital packet  633 C, and convert the fourth upstream protection digital packet  633 C into a fourth upstream protection digital signal  635 C. The fourth upstream protection digital signal  635 C may be transmitted to a fourth protection interface  636 C of the fourth radio unit  604 C. 
         [0134]    In some embodiment, the second wireless controller  609 C of the second radio unit  602 C may encapsulate the second downstream protection digital signal  617 C into the second downstream protection digital packet  618 C addressed to a destination radio unit. The fourth wireless controller  634 C of the fourth radio unit  604 C may decapsulate the fourth upstream protection digital packet  633 C, accept only the upstream protection digital packet addressed to the destination radio unit that includes the fourth wireless controller  634 C, and convert the accepted upstream protection digital packet into the fourth upstream protection digital signal  635 C. 
         [0135]    In some embodiment, the first radio unit  601 C and the third radio unit  603 C may be configured to operate as a vertical polarization protection pair, and the second radio unit  602 C and the fourth radio unit  604 C may be configured to operate as a horizontal polarization protection pair. 
         [0136]    In some embodiment, the first radio unit  601 C and the second radio unit  602 C may be configured as a first XPIC pair, and the third radio unit  603 C and the fourth radio unit  604 C may be configured as a second XPIC pair. 
         [0137]    In some embodiment, the first downstream XPIC IF signal  637 C and the second downstream XPIC IF signal  615 C are configured to use different carrier frequencies within the license-free 60 GHz band. 
         [0138]    In some embodiment, a protection interconnection within any one of the vertical polarization protection pair and the horizontal polarization protection pair and an XPIC interconnection within any one of the first XPIC pair and the second XPIC pair are configured to use different channels allocated within the license-free 60 GHz band. 
         [0139]      FIG. 14  illustrates yet another exemplary embodiment of an all outdoor radios system configured with a protection system and an XPIC application using a wireless channel operating at a license-free 60 GHz band in accordance with the present invention. In the exemplary embodiment  700 C, the all outdoor radios system configured with a protection system and an XPIC application using a wireless channel operating at a license-free 60 GHz band may include: a first radio unit  701 C configured to use vertical polarization, a second radio unit  702 C configured to use horizontal polarization, a third radio unit  703 C configured to use vertical polarization, and a fourth radio unit  704 C configured to use horizontal polarization. The first radio unit  701 C and the second radio unit  702 C are communicatively coupled to an ACU  750 C and the third radio unit  703 C and the fourth radio unit  704 C are communicatively coupled to an ACU  755 C, respectively. The third radio unit  703 C may include a third duplexer  705 C, a third receiver  706 C, a third demodulator  707 C, a third protection interface  708 C, a third wireless controller  709 C, a third modem  710 C, a third IF combiner  711 C, a third IF splitter  712 C, a third transceiver  713 C, and a third 60 GHz antenna  714 C. A third downstream XPIC IF signal  715 C and a third downstream protection IF signal  716 C may be received at the third IF combiner  711 C. The third IF combiner  711 C may combine the third downstream XPIC IF signal  715 C and the third downstream protection IF signal  716 C, and generate a third downstream combined IF signal  719 C. The third downstream combined IF signal  719 C may be transmitted to the third transceiver  713 C. The third transceiver  713 C may convert the third downstream combined IF signal  719 C into a third 60 GHz RF signal  720 C, and amplify the third 60 GHz RF signal  720 C. The amplified third 60 GHz RF signal  720 C may be transmitted to a third 60 GHz antenna  714 C connected to the third transceiver  713 C. 
         [0140]    In some embodiment, a third downstream protection digital signal  717 C may be received at the third protection interface  708 C. The third downstream protection digital signal  717 C may be transmitted to the third wireless controller  709 C. The third wireless controller  709 C may encapsulate the third downstream protection digital signal  717 C into a third downstream protection digital packet  718 C, and transmit the third downstream protection digital packet  718 C to the third modem  710 C. The third modem  710 C may convert the third downstream protection digital packet  718 C into the third downstream protection IF signal  716 C, and transmit the third downstream protection IF signal  716 C to the third IF combiner  711 C. 
         [0141]    In some embodiment, the third 60 GHz RF signal  720 C may be received at a fourth 60 GHz antenna  721 C of the fourth radio unit  704 C. The fourth 60 GHz antenna  721 C may transmit the received third 60 GHz RF signal  720 C to a fourth transceiver  722 C of the fourth radio unit  704 C. The fourth transceiver  722 C may amplify the received third 60 GHz RF signal  720 C, and convert the received third 60 GHz RF signal  720 C into a fourth upstream combined IF signal  723 C. The fourth upstream combined IF signal  723 C may be transmitted to a fourth IF splitter  724 C of the fourth radio unit  704 C. The fourth IF splitter  724 C may extract a fourth upstream XPIC IF signal  725 C from the fourth upstream combined IF signal  723 C, and transmit the fourth upstream XPIC IF signal  725 C to a fourth demodulator  726 C of the fourth radio unit  704 C. The fourth demodulator  726 C may use the fourth upstream XPIC IF signal  725 C to cancel interference of the vertical polarization in the fourth downstream XPIC IF signal  737 C. 
         [0142]    In some embodiment, the third 60 GHz RF signal  720 C may be received at a first 60 GHz antenna  727 C of the first radio unit  701 C. The first 60 GHz antenna  727 C may transmit the received third 60 GHz RF signal  720 C to a first transceiver  728 C of the first radio unit  701 C. The first transceiver  728 C may amplify the received third 60 GHz RF signal  720 C, and convert the received third 60 GHz RF signal  720 C into a first upstream combined IF signal  729 C. The first upstream combined IF signal  729 C may be transmitted to a first IF splitter  730 C of the first radio unit  701 C. The first IF splitter  730 C may extract a first upstream protection IF signal  731 C from the first upstream combined IF signal  729 C. 
         [0143]    In some embodiment, the first upstream protection IF signal  731 C may be transmitted to a first modem  732 C of the first radio unit  701 C. The first modem  732 C may convert the first upstream protection IF signal  731 C into a first upstream protection digital packet  733 C, and transmit the first upstream protection digital packet  733 C to a first wireless controller  734 C of the first radio unit  701 C. The first wireless controller  734 C decapsulates the first upstream protection digital packet  733 C, and converts the first upstream protection digital packet  733 C into a first upstream protection digital signal  735 C. The first upstream protection digital signal  735 C may be transmitted to a first protection interface  736 C of the first radio unit  701 C. 
         [0144]    In some embodiment, the third wireless controller  709 C of the third radio unit  703 C may encapsulate the third downstream protection digital signal  717 C into the third downstream protection digital packet  718 C addressed to a destination radio unit. The first wireless controller  734 C of the first radio unit  701 C may decapsulate the first upstream protection digital packet  733 C, accept only the upstream protection digital packet addressed to the destination radio unit that includes the first wireless controller  734 C, and convert the accepted upstream protection digital packet into the first upstream protection digital signal  735 C. 
         [0145]    In some embodiment, the first radio unit  701 C and the third radio unit  703 C may be configured to operate as a vertical polarization protection pair, and the second radio unit  702 C and the fourth radio unit  704 C may be configured to operate as a horizontal polarization protection pair. 
         [0146]    In some embodiment, the first radio unit  701 C and the second radio unit  702 C may be configured as a first XPIC pair, and the third radio unit  703 C and the fourth radio unit  704 C may be configured as a second XPIC pair. 
         [0147]    In some embodiment, the third downstream XPIC IF signal  715 C and the fourth downstream XPIC IF signal  737 C are configured to use different carrier frequencies within the license-free 60 GHz band. 
         [0148]    In some embodiment, a protection interconnection within any one of the vertical polarization protection pair and the horizontal polarization protection pair and an XPIC interconnection within any one of the first XPIC pair and the second XPIC pair are configured to use different channels allocated within the license-free 60 GHz band. 
         [0149]      FIG. 15  illustrates yet another exemplary embodiment of an all outdoor radios system configured with a protection system and an XPIC application using a wireless channel operating at a license-free 60 GHz band in accordance with the present invention. In the exemplary embodiment  800 C, the all outdoor radios system configured with a protection system and an XPIC application using a wireless channel operating at a license-free 60 GHz band may include: a first radio unit  801 C configured to use vertical polarization, a second radio unit  802 C configured to use horizontal polarization, a third radio unit  803 C configured to use vertical polarization, and a fourth radio unit  804 C configured to use horizontal polarization. The first radio unit  801 C and the second radio unit  802 C are communicatively coupled to an ACU  850 C and the third radio unit  803 C and the fourth radio unit  804 C are communicatively coupled to an ACU  855 C, respectively. The fourth radio unit  804 C may include a fourth duplexer  805 C, a fourth receiver  806 C, a fourth demodulator  807 C, a fourth protection interface  808 C, a fourth wireless controller  809 C, a fourth modem  810 C, a fourth IF combiner  811 C, a fourth IF splitter  812 C, a fourth transceiver  813 C, and a fourth 60 GHz antenna  814 C. A fourth downstream XPIC IF signal  815 C and a fourth downstream protection IF signal  816 C may be received at the fourth IF combiner  811 C. The fourth IF combiner  811 C may combine the fourth downstream XPIC IF signal  815 C and the fourth downstream protection IF signal  816 C, and generate a fourth downstream combined IF signal  819 C. The fourth downstream combined IF signal  819 C may be transmitted to the fourth transceiver  813 C. The fourth transceiver  813  may convert the fourth downstream combined IF signal  819 C into a fourth 60 GHz RF signal  820 C, and amplify the fourth 60 GHz RF signal  820 C. The amplified fourth 60 GHz RF signal  820 C may be transmitted to a fourth 60 GHz antenna  814 C connected to the fourth transceiver  813 C. 
         [0150]    In some embodiment, a fourth downstream protection digital signal  817 C may be received at the fourth protection interface  808 C. The fourth downstream protection digital signal  817 C may be transmitted to the fourth wireless controller  809 C. The fourth wireless controller  809 C may encapsulate the fourth downstream protection digital signal  817 C into a fourth downstream protection digital packet  818 C, and transmit the fourth downstream protection digital packet  818 C to the fourth modem  810 C. The fourth modem  810 C may convert the fourth downstream protection digital packet  818 C into the fourth downstream protection IF signal  816 C, and transmit the fourth downstream protection IF signal  816 C to the first IF combiner  811 C. 
         [0151]    In some embodiment, the fourth 60 GHz RF signal  820 C may be received at a third 60 GHz antenna  821 C of the third radio unit  803 C. The third 60 GHz antenna  821 C may transmit the received fourth 60 GHz RF signal  820 C to a third transceiver  822 C of the third radio unit  803 C. The third transceiver  822 C may amplify the received fourth 60 GHz RF signal  820 C, and convert the received fourth 60 GHz RF signal  820 C into a third upstream combined IF signal  823 C. The third upstream combined IF signal  823 C may be transmitted to a third IF splitter  824 C of the third radio unit  803 C. The third IF splitter  824 C may extract a third upstream XPIC IF signal  825 C from the third upstream combined IF signal  823 C, and transmit the third upstream XPIC IF signal  825 C to a third demodulator  826 C of the third radio unit  803 C. The third demodulator  826 C may use the third upstream XPIC IF signal  825 C to cancel interference of the horizontal polarization in the third downstream XPIC IF signal  837 C. 
         [0152]    In some embodiment, the fourth 60 GHz RF signal  820 C may be received at a second 60 GHz antenna  827 C of the second radio unit  802 C. The second 60 GHz antenna  827 C may transmit the received fourth 60 GHz RF signal  820 C to a second transceiver  828 C of the second radio unit  802 C. The second transceiver  828 C may amplify the received second 60 GHz RF signal  820 C, and convert the received fourth 60 GHz RF signal  820 C into a second upstream combined IF signal  829 C. The second upstream combined IF signal  829 C may be transmitted to a second IF splitter  830 C of the second radio unit  802 C. The second IF splitter  830 C may extract a second upstream protection IF signal  831 C from the second upstream combined IF signal  829 C. 
         [0153]    In some embodiment, the second upstream protection IF signal  831 C may be transmitted to a second modem  832 C of the second radio unit  802 C. The second modem  832 C may convert the second upstream protection IF signal  831 C into a second upstream protection digital packet  833 C, and transmit the second upstream protection digital packet  833 C to a second wireless controller  834 C of the second radio unit  802 C. The second wireless controller  834 C decapsulates the second upstream protection digital packet  833 C, and converts the second upstream protection digital packet  833 C into a second upstream protection digital signal  835 C. The second upstream protection digital signal  835 C may be transmitted to a second protection interface  836 C of the second radio unit  802 C. 
         [0154]    In some embodiment, the fourth wireless controller  809 C of the fourth radio unit  804 C may encapsulate the fourth downstream protection digital signal  817 C into the fourth downstream protection digital packet  818 C addressed to a destination radio unit. The second wireless controller  834 C of the second radio unit  802 C may decapsulate the second upstream protection digital packet  833 C, accept only the upstream protection digital packet addressed to the destination radio unit that includes the second wireless controller  834 C, and convert the accepted upstream protection digital packet into the second upstream protection digital signal  835 C. 
         [0155]    In some embodiment, the first radio unit  801 C and the third radio unit  803 C may be configured to operate as a vertical polarization protection pair, and the second radio unit  802 C and the fourth radio unit  804 C may be configured to operate as a horizontal polarization protection pair. 
         [0156]    In some embodiment, the first radio unit  801 C and the second radio unit  802 C may be configured as a first XPIC pair, and the third radio unit  803 C and the fourth radio unit  804 C may be configured as a second XPIC pair. 
         [0157]    In some embodiment, the third downstream XPIC IF signal  837 C and the fourth downstream XPIC IF signal  815 C are configured to use different carrier frequencies within the license-free 60 GHz band. 
         [0158]    In some embodiment, a protection interconnection within any one of the vertical polarization protection pair and the horizontal polarization protection pair and an XPIC interconnection within any one of the first XPIC pair and the second XPIC pair are configured to use different channels allocated within the license-free 60 GHz band. 
         [0159]      FIG. 16  illustrates an exemplary method performed by an all outdoor radios system configured with an XPIC application using a wireless channel operating at a license-free 60 GHz band in accordance with the present invention. The method includes: step  901 C for receiving a first downstream XPIC IF signal at a first receiver of a first radio unit; step  902 C for transmitting the first downstream XPIC IF signal to a first demodulator of the first radio unit and a first transceiver of the first radio unit, respectively; step  903 C for converting the first downstream XPIC IF signal into a first 60 GHz RF signal, and amplifying the first 60 GHz RF signal at the first transceiver of the first radio unit; step  904 C for transmitting the first 60 GHz RF signal at a first 60 GHz antenna of the first radio unit; step  905 C for receiving the first 60 GHz RF signal at a second 60 GHz antenna of a second radio unit; step  906 C for amplifying the first 60 GHz RF signal, and converting the first 60 GHz RF signal into a second upstream XPIC IF signal at a second transceiver of the second radio unit; and step  907 C for transmitting the second upstream XPIC IF signal to a second demodulator of the second radio unit. 
         [0160]      FIG. 17  illustrates another exemplary method performed by an all outdoor radios system configured with an XPIC application using a wireless channel operating at a license-free 60 GHz band in accordance with the present invention. The method includes: step  1001 C for receiving a second downstream XPIC IF signal at a second receiver of the second radio unit; step  1002 C for transmitting the second downstream XPIC IF signal to the second demodulator of the second radio unit and the second transceiver of the second radio unit, respectively; step  1003 C for converting the second downstream XPIC IF signal into a second 60 GHz RF signal, and amplifying the second 60 GHz RF signal at the second transceiver of the second radio unit; step  1004 C for transmitting the second 60 GHz RF signal at the second 60 GHz antenna of the second radio unit; step  1005 C for receiving the second 60 GHz RF signal at the first 60 GHz antenna of the first radio unit; step  1006 C for amplifying the second 60 GHz RF signal, and converting the second 60 GHz RF signal into a first upstream XPIC IF signal at the first transceiver of the first radio unit; and step  1007 C for transmitting the first upstream XPIC IF signal to the first demodulator of the first radio unit. 
         [0161]      FIG. 18  illustrates an exemplary method performed by an all outdoor radios system configured with a protection system and an XPIC application using a wireless channel operating at a license-free 60 GHz band in accordance with the present invention. The method includes: step  1101 C for receiving a first downstream XPIC IF signal at a first IF combiner of a first radio unit; step  1102 C for receiving a first downstream protection IF signal at the first IF combiner of the first radio unit; step  1103 C for combining the first downstream XPIC IF signal and the first downstream protection IF signal, and generating a first downstream combined IF signal at the first IF combiner of the first radio unit; step  1104 C for converting the first downstream combined IF signal into a first 60 GHz RF signal, and amplifying the first 60 GHz RF signal at a first transceiver of the first radio unit; step  1105 C for transmitting the first 60 GHz RF signal at a first 60 GHz antenna of the first radio unit; step  1106 C for receiving the first 60 GHz RF signal at a second 60 GHz antenna of a second radio unit; step  1107 C for amplifying the first 60 GHz RF signal, and converting the first 60 GHz RF signal into a second upstream combined IF signal at a second transceiver of the second radio unit; step  1108 C for extracting a second upstream XPIC IF signal from the second upstream combined IF signal at a second IF splitter of the second radio unit; step  1109 C for transmitting the second upstream XPIC IF signal to a second demodulator of the second radio unit; step  1110 C for receiving the first 60 GHz RF signal at a third 60 GHz antenna of a third radio unit; step  1111 C for amplifying the first 60 GHz RF signal, and converting the first 60 GHz RF signal into a third upstream combined IF signal at a third transceiver of the third radio unit; step  1112 C for extracting a third upstream protection IF signal from the third upstream combined IF signal at a third IF splitter of the third radio unit; and step  1113 C for converting the third upstream protection IF signal into a third upstream protection digital signal and transmit it to a third protection interface. 
         [0162]      FIG. 19  illustrates another exemplary method performed by an all outdoor radios system configured with a protection system and an XPIC application using a wireless channel operating at a license-free 60 GHz band in accordance with the present invention. The method includes: step  1201 C for receiving a second downstream XPIC IF signal at a second IF combiner of the second radio unit; step  1202 C for receiving a second downstream protection IF signal at the second IF combiner of the second radio unit; step  1203 C for combining the second downstream XPIC IF signal and the second downstream protection IF signal, and generating a second downstream combined IF signal at a second IF combiner of the second radio unit; step  1204 C for converting the second downstream combined IF signal into a second 60 GHz RF signal, and amplifying the second 60 GHz RF signal at the second transceiver of the second radio unit; step  1205 C for transmitting the second 60 GHz RF signal at the second antenna of the second radio unit; step  1206 C for receiving the second 60 GHz RF signal at the first antenna of the first radio unit; step  1207 C for amplifying the second 60 GHz RF signal, and converting the second 60 GHz RF signal into a first upstream combined IF signal at the first transceiver of the first radio unit; step  1208 C for extracting a first upstream XPIC IF signal from the first upstream combined IF signal at a first IF splitter of the first radio unit; step  1209 C for transmitting the first upstream XPIC IF signal to a first demodulator of the first radio unit; step  1210 C for receiving the second 60 GHz RF signal at a fourth antenna of a fourth radio unit; step  1211 C for amplifying the second 60 GHz RF signal, and converting the second 60 GHz RF signal into a fourth upstream combined IF signal at a fourth transceiver of the fourth radio unit; step  1212 C for extracting a fourth upstream protection IF signal from the fourth upstream combined IF signal at a fourth IF splitter of the fourth radio unit; and step  1213 C for converting the fourth upstream protection IF signal into a fourth upstream protection digital signal and transmit it to a fourth protection interface. 
         [0163]      FIG. 20  illustrates yet another exemplary method performed by an all outdoor radios system configured with a protection system and an XPIC application using a wireless channel operating at a license-free 60 GHz band in accordance with the present invention. The method includes: step  1301 C for receiving a third downstream XPIC IF signal at a third IF combiner of the third radio unit; step  1302 C for receiving a third downstream protection IF signal at the third IF combiner of the third radio unit; step  1303 C for combining the third downstream XPIC IF signal and the third downstream protection IF signal, and generating a third downstream combined IF signal at the third IF combiner of the third radio unit; step  1304 C for converting the third downstream combined IF signal into a third 60 GHz RF signal, and amplifying the third 60 GHz RF signal at the third transceiver of the third radio unit; step  1305 C for transmitting the third 60 GHz RF signal at the third antenna of the third radio unit; step  1306 C for receiving the third 60 GHz RF signal at the fourth antenna of the fourth radio unit; step  1307 C for amplifying the third 60 GHz RF signal, and converting the third 60 GHz RF signal into a fourth upstream combined IF signal at the fourth transceiver of the fourth radio unit; step  1308 C for extracting a fourth upstream XPIC IF signal from the fourth upstream combined IF signal at the fourth IF splitter of the fourth radio unit; step  1309 C for transmitting the fourth upstream XPIC IF signal to a fourth demodulator of the fourth radio unit; step  1310 C for receiving the third 60 GHz RF signal at the first antenna of the first radio unit; step  1311 C for amplifying the third 60 GHz RF signal, and converting the third 60 GHz RF signal into the first upstream combined IF signal at the first transceiver of the first radio unit; step  1312 C for extracting a first upstream protection IF signal from the first upstream combined IF signal at the first IF splitter of the first radio unit; and step  1313 C for converting the first upstream protection IF signal into a first upstream protection digital signal and transmit it to a first protection interface. 
         [0164]      FIG. 21  illustrates yet another exemplary method performed by an all outdoor radios system configured with a protection system and an XPIC application using a wireless channel operating at a license-free 60 GHz band in accordance with the present invention. The method includes: step  1401 C for receiving a fourth downstream XPIC IF signal at a fourth IF combiner of the fourth radio unit; step  1402 C for receiving a fourth downstream protection IF signal at the fourth IF combiner of the fourth radio unit; step  1403 C for combining the fourth downstream XPIC IF signal and the fourth downstream protection IF signal, and generating a fourth downstream combined IF signal at a fourth IF combiner of the fourth radio unit; step  1404 C for converting the fourth downstream combined IF signal into a fourth 60 GHz RF signal, and amplifying the fourth 60 GHz RF signal at the fourth transceiver of the fourth radio unit; step  1405 C for transmitting the fourth 60 GHz RF signal at the fourth antenna of the fourth radio unit; step  1406 C for receiving the fourth 60 GHz RF signal at the third antenna of the third radio unit; step  1407 C for amplifying the fourth 60 GHz RF signal, and converting the fourth 60 GHz RF signal into the third upstream combined IF signal at the third transceiver of the third radio unit; step  1408 C for extracting a third upstream XPIC IF signal from the third upstream combined IF signal at the third IF splitter of the third radio unit; step  1409 C for transmitting the third upstream XPIC IF signal to a third demodulator of the third radio unit; step  1410 C for receiving the fourth 60 GHz RF signal at the second antenna of the second radio unit; step  1411 C for amplifying the fourth 60 GHz RF signal, and converting the fourth 60 GHz RF signal into the second upstream combined IF signal at the second transceiver of the second radio unit; step  1412 C for extracting the second upstream protection IF signal from the second upstream combined IF signal at the second IF splitter of the second radio unit; and step  1413 C for converting the second upstream protection IF signal into a second upstream protection digital signal and transmit it to a second protection interface. 
         [0165]    It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.