Patent Publication Number: US-2004047335-A1

Title: Wireless local area network extension using existing wiring and wireless repeater module(s)

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
     [0001] This application is related to and claims priority from pending U.S. Provisional Application Nos. 60/390,091 and 60/390,094, filed on Jun. 21, 2002, the contents of which are incorporated herein by reference. 
    
    
     
       FIELD OF THE INVENTION  
       [0002] The present invention relates generally to wireless communications, and particularly to wireless local area networks.  
       BACKGROUND OF THE INVENTION  
       [0003] Several standard protocols for wireless local area networks, commonly referred to as WLANs, are becoming popular. These include protocols such as 802.11 (as set forth in the 802.11 wireless standards), home RF, and Bluetooth. The standard wireless protocol with the most commercial success to date is the 802.11b protocol.  
       [0004] While the specifications of products utilizing the above standard wireless protocols commonly indicate data rates on the order of, for example, 11 MBPS and ranges on the order of, for example, 100 meters, these performance levels are rarely, if ever, realized. This lack of performance is due to attenuation of the radiation paths of RF signals, which are typically in the range of 2.4 GHz, in an indoor environment. Base to receiver ranges are generally less than the coverage range required in a typical home, and may be as little as 10 to 15 meters. Further, in structures that have split floor plans, such as ranch style or two story homes, or that are constructed of materials that attenuate RF signals, areas in which wireless coverage is needed may be physically separated by distances outside of the range of, for example, an 802.11 protocol based system. Finally, the data rates of the above standard wireless protocols are dependent on the signal strength. As distances in the area of coverage increase, wireless system performance typically decreases.  
       [0005] Therefore, what is needed is a way to extend WLAN coverage in environments in which coverage is normally limited.  
       SUMMARY OF THE INVENTION  
       [0006] Accordingly, the present invention provides an interface unit that extends coverage in a wireless environment such as a WLAN environment. The interface unit is cabled to a transceiver, such as an 802.11 access point and includes a matching circuit that interfaces with, for example, the wiring of a standard wall power outlet, or with other cabling or wiring present within a structure, and that couples 802.11 signals transmitted to and received from the access point over the wiring with no translation in RF frequency.  
       [0007] The interface unit may be a bidirectional unit capable of utilizing a switched receive and transmit amplification of signals to and from the access point. However, an increased signal level may only be needed on the return link, as the strength of a signal transmitted from a WLAN transceiver device such as a network device is typically significantly less than that of a signal transmitted from the access point, as a network device is typically battery operated and therefore minimization of power consumption is a key consideration. Therefore, the signal may be received by the access point over a wired connection to the wiring, and a receive only module may be located near the network device.  
       [0008] In another embodiment, the interface unit may provide an up/down conversion function that provides for the interface to the wiring at an intermediate frequency. Note that a bi-directional amplification capability may be used regardless of whether an up/down conversion is executed. Since WLAN protocols are typically time division duplex based protocols, the amplification need only be in a single direction at any given time. Therefore, the amplification may normally be enabled in one direction, and, when a sufficient signal is detected in the other direction, the first direction of amplification will be disabled and the opposite direction of amplification enabled.  
       [0009] The above amplification may be performed with a single switched amplifier or with two amplifiers that are enabled or disabled. However, a single switched amplifier is the preferred embodiment, as it provides for a reduced product cost. The detection process may be executed by a simple band-limited power detector. The “normal direction” of amplification will be from the antenna to the wired network for all modules, as the RF signal coupled to the antenna will be weaker than the re-amplified signal from the wires.  
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0010]FIG. 1 is a schematic drawing showing a wireless wide area network including an interface unit to extend the range of the network.  
     [0011]FIG. 2 is a schematic drawing of the interface unit of FIG. 1.  
     [0012]FIG. 3 is a schematic drawing of a bi-directional amplification circuit within the interface unit of FIG. 2.  
     [0013]FIG. 4 is schematic of an alternative amplification circuit.  
     [0014]FIG. 5 is a schematic drawing of a switchable amplification circuit.  
     [0015]FIG. 6 is a schematic drawing of an alternative switchable amplification circuit.  
     [0016]FIG. 7 is a more detailed schematic of cable/wiring interface electronics used with the interface unit of FIG. 1.  
     [0017]FIG. 8 shows a wireless wide area network similar to that shown in FIG. 1 but including multiple interface units.  
     [0018]FIG. 9 is a schematic of an interface unit utilizing up and down conversion of a wireless wide area network signal to an intermediate frequency.  
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0019] Referring to FIG. 1, an exemplary wireless local area network (WLAN) is shown at  99 . The WLAN  99  includes a wireless gateway (access point)  100  connected to a wide area connection  101 . The access point  100  transmits signals, such as RF signals, to exemplary network devices  104 ,  105  which may be any type of wireless communication devices capable of transmitting and/or receiving RF signals transmitting IEEE 802.11 packets or, alternatively, signals based on Bluetooth, Hyperlan, or other wireless communication protocols. However, for purposes of discussion, these signals will be referred to as RF signals. Propagation paths to each of the network devices  104 ,  105  are shown as signal paths  102 ,  103 , respectively. Here, the RF signal carried over the signal path  102  is sufficient to maintain high speed data packet communications. However, the signal path  103  attenuates an RF signal intended for the network device  105  to a point where few, if any, data packets are received in either direction.  
     [0020] Still referring to FIG. 1, an interface unit  200 , may also known as an interface module, distribution node or, more specifically, a power interface unit when it is connected to existing wiring  201  within a structure  108  such as an office building or a home. Those of ordinary skill in the art will recognize that the interface unit  200  may be connected to other suitable wiring in a structure, including but not limited to Ethernet cable, power lines, CAT5 cable, television cable, coaxial cable, telephone wires or the like. However, for purposes of discussion, the wiring  201  will be referred to throughout as structural wiring  201 .  
     [0021] The interface unit  200  takes an RF signal interfaced from access point  100  by a cable (interface cable)  110  and receives and transmits the RF signal over the structural wiring  201 . The RF signal is then radiated from the structural wiring  201  based on the natural radiation properties of the power lines  20  to establish a communication link between the access point  100  and the network device  105 . Preferably, no intermediate frequency is used to establish the communication link. Instead, the RF signal is maintained at the original frequency carrier as if the signal is transmitted wirelessly on the signal path  103 .  
     [0022] The interface unit  200  may also be designed to amplify RF signals in one or both directions to or from the network device  105 . If the interface unit  200  amplifies these RF signals in both directions, the amplification function in each direction may only be enabled in one direction at a time based on a power threshold detection circuit (not shown) as is well known to those skilled in the art. Power detectors, network devices and access points are described in detail in pending International Application No. PCT/US 03/16208, which claims priority from Provisional Patent Application No. 60/390,093, the contents of which are incorporated by reference herein. The transmitted signal from the access point  100  will trigger the amplification process in the outbound direction. When there is no access point signal present, the amplification direction will be from the structural wiring  201  to the access point  100 .  
     [0023]FIG. 2 shows the interface unit  200  in exemplary form. The interface unit  200  includes an electronics housing  700 , and is powered by and coupled to the structural wiring  201  in FIG. 1 via a well known power plug connecter  701 . More specifically, the prongs of the power plug connector  701  are insertable into a power receptacle  703  of a conventional wall power outlet  702  to which the structural wiring  201  (FIG. 1) is connected.  
     [0024] Referring to FIG. 3, components of a bi-directional amplification circuit  599  are shown. These components are contained within the electronics housing  700  shown in FIG. 3. Specifically, an antenna  600  is for receiving a WLAN RF signal and a detector  603  is for detecting the presence of the RF signal by comparing power levels on either side of the amplification circuit  599 . The detector  603  may also compare the value of a detected signal with an absolute threshold, which may be relative to, for example, thermal noise or ambient noise. When the detector  603  does detect the presence of the RF signal, a selector  604 , which may be a settable switch well known to those skilled in the art, sets an amplifier module  601  to amplify the RF signal on the structural wiring  201  in a predetermined direction. The amplified RF signal is then coupled to the structural wiring  201  by cable interface electronics  602 , which are described in detail below in association with FIG. 8. When the RF signal is present at the structural wiring  201  rather than at the antenna  600 , meaning that the RF signal is being received from the structural wiring  201 , the detector  603  sets the selector  604  to amplify the RF signal in a direction opposite to that described above and to transmit the amplified RF signal on the antenna  600 .  
     [0025] Referring now to FIG. 4, two separate bi-directional amplification circuits  599   a ,  599   b  may be used instead of the single bi-directional amplification circuit  599  in FIG. 3. In FIG. 4, the bi-directional amplification circuit  599   a  is, for example, a transmitting bi-directional amplification circuit, while the bi-directional amplification circuit  599   b  is, for example, a receiving bi-directional amplification circuit relative to the structural wiring  201 .  
     [0026] In this exemplary configuration, in the bi-directional amplification circuit  599   b , an RF signal is received on an antenna  556  from the access point  100  or from the network device  105  (FIG. 1). The RF signal is coupled from the antenna  556  to the amplifier  557  where it is amplified. The RF signal is then passed through cable interface electronics  558  and then to structural wiring  201 .  
     [0027] In the bi-directional amplification circuit  599   a , the RF signal received from the structural wiring  201  is coupled to cable interface electronics  550  and then amplified by an amplifier  551 . The amplified RF signal is then coupled to an antenna  555  for transmission to the access point  100  (FIG. 1) or to another WLAN device.  
     [0028] Turning now to FIG. 5, the bi amplifier module  601  of FIG. 3 is shown in more detail. When the selector  604  is set for left to right amplification, switches  501 ,  503  are set such that an RF signal at an input/output  500  is coupled to an amplifier  505  and then to an input/output  504 . When the selector  604  is set for right to left amplification, the switches  501 ,  503  are set such that the RF signal at the input/output  504  is coupled to an amplifier  502  and then to the input/output  500 .  
     [0029] In an alternative amplifier module  601 ′ shown in FIG. 6, more switches may be used so that a single amplifier may be used for multiple paths. For example, when a control line  408  corresponding to the selector  604  in FIGS. 3 and 5 is set for left to right amplification, switches  401 ,  402  are set to couple the RF signal input from input/output  400  to an amplifier  403 . Switches  404 ,  405  are then set to couple the RF signal output from the amplifier  403  to an input/output  409 .  
     [0030] When the selector line  408  is set for right to left amplification, the switches  401 ,  402 ,  404 , and  405  are set so that the RF signal is input into the amplifier  403  over trace  407 . The amplified RF signal is then output over trace  406  to the input/output  400 .  
     [0031]FIG. 7 shows exemplary components of the cable interface electronics  602 ,  550 ,  558  of FIGS. 3 and 4 in more detail. The cable interface electronics provide a connection and impedance matching function between the amplification circuits and the structural wiring  201 . In FIG. 7, the structural wiring  201  is connected to an interface connector  651 , which could be the prongs of the power plug connector  701  shown in FIG. 2. The RF signal is then matched using a matching circuit  652  before being coupled to a filter  653 . The matching circuit  652  is well known to those of ordinary skill in the art and allows for the best and most efficient transfer of the RF signal to and from the structural wiring  201  and the cable interface electronics. Matching impedance is typically set based on pre-known cable impedance values. For instance, coaxial cable impedance is known to be 75 Ohms. The filter  653  removes unwanted out of band noise from the RF signal to be transferred to or from the amplification circuits via cable interface electronics output  654 , and is also well known to those of ordinary skill in the art. The bandwidth of the filter is simply matched to the desired RF or IF band of interest, such as 802.11, and excludes or attenuates signals outside that band.  
     [0032] Referring now to FIG. 8, an exemplary wireless local area network (WLAN)  99 ′ is essentially the same as that shown FIG. 1 except that an additional interface unit  200 ′ is included. The interface unit  200 ′ couples the RF signal from the structural wiring  201  to an RF path or connection  203 . The RF signal is passed to and/or from the RF connection  203  by another network device  105 . In this manner, a second interface unit  200 ′ further extends the WLAN  99 ′.  
     [0033] The interface units  200 ,  200 ′ may be designed to amplify an RF signal in one or both directions to or from the network device  105 . If the interface units  200 ,  200 ′ are designed to perform both functions, the amplification circuit may only be enabled in one direction at a time based on power threshold detection as described above. The transmitted signal from the access point  100  will trigger the amplification process in the outbound direction. When there is no access point signal present, the amplification will be triggered in a direction from the antenna  600  (FIG. 3) to the structural wiring  201 .  
     [0034] Referring to FIG. 9, when an intermediate frequency is used to pass the signals over the structural wiring  201 , the interface unit  200  may provide an up/down conversion function as well. FIG. 9 shows the up conversion function as, for example, IF signals are passed from the structural wiring  201  over a connector  661 . The IF signal is then coupled to matching electronics  662 . Next, a LO frequency is generated by obtaining the 60 Hz power signal from the structural wiring  201  as a reference for a phase locked loop or other well known synthesizer. This is done by obtaining the power signal from the matching circuit  662 , filtering it in a filter  667  and synthesizing the LO via a synthesizer  668 . The IF signal is then also coupled from the matching circuit  662  to the filter  663  and then up (or down converted) by a frequency converter  664 . The output of the frequency converter  664  is connected to a filter  665  and then to input/output  666 . Alternatively, the IF signal may be passed in the other direction, from the input/output  666  to the structural wiring  201  using the same process.  
     [0035] The invention has been described in detail with particular references to presently preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.