PATENT DOCUMENT

Publication Number: US-8660035-B2
Application Number: US-9279706-A
Country: US
Kind Code: B2

Title: Wireless relay network media access control layer control plane system and method

Abstract:
A method and system for using a communication network having a relay node to provide wireless communication with a mobile station. A ranging region is established with the mobile station in which the establishment of the ranging region includes the transmission of control information corresponding to the relay node. The mobile station is allowed to enter the communication network. The relay node is used to wirelessly communicate with the mobile station in at least one of the uplink and downlink directions.

Claims:
The invention claimed is: 
     
       1. A method for using a communication network having a relay node to provide wireless communication with a mobile station, the method comprising:
 establishing a ranging region with the mobile station, the establishment of the ranging region including the transmission of control information corresponding to the relay node, and responsive to the control information, transmitting, by the relay node, a code to a base station to indicate to the base station that the relay node has been selected by the mobile station from a plurality of relay nodes; 
 allowing the mobile station to enter the communication network; using the relay node to wirelessly communicate directly with the mobile station in an uplink direction; and using the base station to bypass the relay node to communicate directly with the mobile station in a downlink direction. 
 
     
     
       2. The method according to  claim 1 , further comprising using the relay node to provide wireless communication service with the mobile station in a base station coverage hole. 
     
     
       3. The method according to  claim 1 , further comprising using the relay node to provide wireless communication service with the mobile station at an outer region of a base station coverage region. 
     
     
       4. The method according to  claim 1 , further comprising using the relay node to supplement the wireless communication capacity of a base station in a corresponding base station coverage region. 
     
     
       5. The method according to  claim 1 , further comprising using the relay node as an air protocol translation device to translate between a first protocol used between the mobile station and the relay node, and a second protocol used between the relay node and a base station, the first protocol being different than the second protocol. 
     
     
       6. The method according to  claim 1 , wherein establishing a ranging region with the mobile station includes providing a common access point switch ranging region. 
     
     
       7. The method according to  claim 1 , wherein allowing the mobile station to enter the network includes monitoring a down link channel description message and an uplink channel description message for information related to the relay node. 
     
     
       8. The method according to  claim 7 , wherein allowing the mobile station to enter the network further includes selecting an access point, the access point being one of a relay node and a base station. 
     
     
       9. The method according to  claim 1 , wherein a frame structure for using the relay node to wirelessly communicate with the mobile station in at least one of the uplink and downlink directions includes a downlink sub frame and an uplink sub frame, a portion of the downlink sub frame being allocated for communication to the mobile station from the relay node and a portion of the uplink sub frame being allocated for communication to the relay node from the mobile station. 
     
     
       10. The method according to  claim 9 , wherein the portion of the downlink sub frame allocated for communication to the mobile station from the relay node includes resource allocation signaling mapping information. 
     
     
       11. The method according to  claim 1 , further comprising handing off communication to a selected target relay node based on a macro diversity set, the macro diversity set including a list of potential target relay nodes for communication hand off. 
     
     
       12. The method according to  claim 11 , wherein the target relay node is in a same base station coverage region as the relay node. 
     
     
       13. The method according to  claim 11 , wherein the target relay node is in a different base station coverage region as the relay node. 
     
     
       14. The method according to  claim 1 , further comprising performing flow control with the relay node to facilitate hand off, the flow control being based on at least one of an upper bound of a communication data rate with the relay node and a hand off action time. 
     
     
       15. The method according to  claim 1 , further comprising establishing MAC management messages for communication with a relay node, the MAC management messages including messages corresponding to configuration, traffic scheduling, flow control, network entry and access point switching messages. 
     
     
       16. A system for wirelessly communicating with a mobile station, the system comprising:
 a relay node, the relay node configured to: 
 monitor a common initial ranging region, a common access point switch ranging region and a private ranging region to range with the mobile station; 
 range with the mobile station; 
 use MAC control plane messages to establish wireless communications with the mobile station; and 
 wirelessly communicate with the mobile station in the an uplink direction, the relay node being bypassed in a downlink direction between a base station and the mobile station. 
 
     
     
       17. The system according to  claim 16 , wherein the relay node is configured to provide wireless communication service with the mobile station in a base station coverage hole. 
     
     
       18. The system according to  claim 16 , further comprising using the relay node to provide wireless communication service with the mobile station at an outer region of a base station coverage region. 
     
     
       19. The system according to  claim 16 , wherein the relay node is configured to supplement the wireless communication capacity of a base station in a corresponding base station coverage region. 
     
     
       20. The system according to  claim 16 , wherein the system further includes a base station, and the relay node configured to translate between a first protocol used between the mobile station and the relay node, and a second protocol used between the relay node and a base station, the first protocol being different than the second protocol. 
     
     
       21. The system according to  claim 16 , wherein the relay node is configured to use a frame to wirelessly communicate with the mobile station in at least one of the uplink and downlink directions, the frame including a downlink sub frame and an uplink subframe, a portion of the downlink sub frame being allocated for communication to the mobile station from the relay node and a portion of the uplink subframe being allocated for communication to the relay node from the mobile station. 
     
     
       22. The system according to  claim 21 , wherein the portion of the downlink sub frame allocated for communication to the mobile station from the relay node includes resource allocation signaling mapping information. 
     
     
       23. The system according to  claim 16 , wherein the relay node is configured to perform flow control with one of another relay node and a base station to facilitate hand off, the flow control being based on at least one of an upper bound of a communication data rate with the relay node and a hand off action time. 
     
     
       24. The system according to  claim 16 , wherein the relay node is configured to use MAC management messages for communication, the MAC management messages including messages corresponding to configuration, traffic scheduling, flow control, network entry and access point switching messages. 
     
     
       25. The system according to  claim 16 , wherein the base station is in communication with the relay node, and the relay node is configured to use MAC messages to communicate MAC control plane information, the MAC messages including at least one of messages corresponding to configuration, traffic scheduling, flow control, network entry and access point switching messages. 
     
     
       26. The method of  claim 1 , wherein, responsive to receiving the code from the relay node, the base station transmits a RNG-RSP message directly to the mobile station. 
     
     
       27. The method of  claim 26 , wherein, responsive to receiving the RNG-RSP message from the base station, the mobile station transmits a ranging code assigned by the relay node to the relay node. 
     
     
       28. The method of  claim 27 , wherein, responsive to receiving the ranging code from the mobile station, the relay node transmits an RNG-RSP response message to the mobile station. 
     
     
       29. A relay node, comprising:
 a process configured to:
 monitor a common initial ranging region, a common access point switch ranging region and a private ranging region to range with the mobile station; 
 range with a mobile station; 
 use MAC control plane messages to establish wireless communications with the mobile station; and 
 wirelessly communicate with the mobile station in the an uplink direction, the relay node being bypassed in a downlink direction between a base station and the mobile station. 
 
 
     
     
       30. The relay node of  claim 29 , wherein the processor is configured to monitor a first ranging region and monitor a second ranging region during establishment of the uplink communication between the wireless mobile station and the relay node, the first ranging region being different from the second ranging region.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Submission Under 35 U.S.C. §371 for U.S. National Stage Patent Application of International Application Number: PCT/CA2006/001842, filed 10 Nov. 2006, entitled WIRELESS RELAY NETWORK MEDIA ACCESS CONTROL LAYER CONTROL PLANE SYSTEM AND METHOD, which is related to and claims priority to U.S. Patent Application Ser. No. 60/735,706, filed 10 Nov. 2005, the entirety of all of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Statement of the Technical Field 
     The present invention relates to the field of wireless communications and more particularly to a method and system for providing a media access control (“MAC”) layer control plane for wireless relay networks. 
     2. Description of the Related Art 
     As the demand for high speed broadband networking over wireless communication links increases, so too does the demand for different types of networks that can accommodate high speed wireless networking. For example, the deployment of IEEE 802.11 wireless networks in homes and business to create Internet access “hot spots” has become prevalent in today&#39;s society. However, these IEEE 802.11-based networks are limited in bandwidth as well as distance. For example, maximum typical throughput from a user device to a wireless access point is 54 MB/sec. at a range of only a hundred meters or so. In contrast, while wireless range can be extend through other technologies such as cellular technology, data throughput using current cellular technologies is limited to a few MB/sec. Put simply, as the distance from the base station increase, the need for higher transmission power increases and the maximum data rate typically decreases. As a result, there is a need to support high speed wireless connectivity beyond a short distance such as within a home or office. 
     As a result of the demand for longer range wireless networking, the IEEE 802.16 standard was developed. The IEEE 802.16 standard is often referred to as WiMAX or less commonly as WirelessMAN or the Air Interface Standard. This standard provides a specification for fixed broadband wireless metropolitan access networks (“MAN”s) that use a point-to-multipoint architecture. Such communications can be implemented, for example, using orthogonal frequency division multiplexing (“OFDM”) communication. OFDM communication uses a spread spectrum technique distributes the data over a large number of carriers that are spaced apart at precise frequencies. This spacing provides the “orthogonality” that prevents the demodulators from seeing frequencies other than their own. 
     The 802.16 standard supports high bit rates in both uploading to and downloading from a base station up to a distance of 30 miles to handle such services as VoIP, IP connectivity and other voice and data formats. Expected data throughput for a typical WiMAX network is 45 MBits/sec. per channel. The 802.16e standard defines a media access control (“MAC”) layer that supports multiple physical layer specifications customized for the frequency band of use and their associated regulations. However, the 802.16e standard does not provide support for multi-hop networks. 
     802.16 networks, such as 802.16j networks, can be deployed as multi-hop networks from the subscriber equipment to the carrier base station. In other words, in multi-hop networks, the subscriber device can communicate with the base station directly or through an intermediate device. 
     The complexity involved in supporting multi-hop networks in a robust manner necessarily involves sophisticated MAC control layer protocols. Such protocols do not exist. For example, as noted above, the IEEE 802.16e standard does not support multi-hop networks. The IEEE 802.16j standard for supporting multi-hop networks has been proposed, but the standard currently makes no provision for MAC layer control plane support. 
     It is therefore desirable to have method and system that provides MAC control plane functions to support wireless multi-hop relay networks, including but not limited to those operating in accordance with the IEEE 802.16 standards. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect, the present invention provides a method for using a communication network having a relay node to provide wireless communication with a mobile station. A ranging region is established with the mobile station in which the establishment of the ranging region includes the transmission of control information corresponding to the relay node. The mobile station is allowed to enter the communication network. The relay node is used to wirelessly communicate with the mobile station in at least one of the uplink and downlink directions. 
     In accordance with another aspect, the present invention provides a system for wirelessly communicating with a mobile station. A stationary relay node ranges with the mobile station, uses MAC control plane messages to establish wireless communications with the mobile station and wirelessly communicates with the mobile station in at least one of the uplink and downlink directions. 
     In accordance with another aspect, the present invention provides a method for wireless communication using a relay node in which a frame structure is implemented for communication with the relay node. The frame structure includes a downlink sub-frame and an uplink sub-frame. At least a portion of one of the downlink sub-frame and the uplink sub-frame is used to communication with the relay node. 
     Additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The aspects of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute part of this specification, illustrate embodiments of the invention and together with the description, serve to explain the principles of the invention. The embodiments illustrated herein are presently preferred, it being understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown, wherein: 
         FIG. 1  is a diagram of a system constructed in accordance with the principles of the present invention; 
         FIG. 2  is a block diagram of a first operational embodiment of the present invention; 
         FIG. 3  is a block diagram of a second operational embodiment of the present invention; 
         FIG. 4  is a block diagram of a third operational embodiment of the present invention; 
         FIG. 5  is a block diagram of a fourth operational embodiment of the present invention; 
         FIG. 6  is a block diagram of a fifth operational embodiment of the present invention; 
         FIG. 7  is a flow chart of an initial network entry process for a mobile station described from the point of view of the mobile station in the operational embodiments shown in  FIGS. 2 and 4 ; 
         FIG. 8  is a flow chart of an initial network entry process for a mobile station described from the point of view of a relay node in the operational embodiments shown in  FIGS. 2 and 4 ; 
         FIG. 9  is a flow chart of an initial network entry process for a mobile station described from the point of view of a base station in the operational embodiments shown in  FIGS. 2 and 4 ; and 
         FIG. 10  is a diagram of an exemplary logical frame structure constructed in accordance with the principles of the present invention; 
         FIG. 11  is a diagram with examples of downlink traffic transmission arrangements; 
         FIG. 12  is a block diagram of a macro diversity intra-base station switching arrangement constructed in accordance with the principles of the present invention; 
         FIG. 13  is a flow chart of an intra-base station switching process from the perspective of a mobile station; 
         FIG. 14  is a flow chart of an intra-base station switching process from the perspective of a relay node; 
         FIG. 15  is a flow chart of an intra-base station switching process from the perspective of a base station; 
         FIG. 16  is a block diagram of a macro diversity inter-base station switching arrangement constructed in accordance with the principles of the present invention; 
         FIG. 17  is a flow chart of an inter-base station switching process from the perspective of a relay node; and 
         FIG. 18  is a flow chart of an inter-base station switching process from the perspective of a base station. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As an initial matter, reference may be made herein to “data plane” and “control plane.” In general, the control plane includes configured or signaled information that determines the overall behavior, mappings, resource allocation and forwarding parameters that can be applied to all connection frames or frames of a service class. Such information is typically established and used to set up the network devices before any payload traffic is transmitted. Data plane refers to the frame processing functions that typically take place in real-time on a frame-by-frame basis. 
     In accordance with embodiments of the invention various MAC control plane embodiments for use in wireless networks using relays are described. While certain embodiments are discussed in the context of wireless networks operating in accordance with the IEEE 802.16 broadband wireless standard, which is hereby incorporated by reference, the invention is not limited in this regard and may be applicable to other broadband networks including those operating in accordance with other OFDM orthogonal frequency division (“OFDM”)-based systems including the 3rd Generation Partnership Project (“3GPP”) and 3GPP2 evolutions. Similarly, the present invention is not limited solely to OFDM-based systems and can be implemented in accordance with other system technologies, e.g., CDMA. 
     Referring now to the drawing figures in which like reference designators refer to like elements, there is shown in  FIG. 1 , a system constructed in accordance with the principles of the present invention and designated generally as “ 10 .” System  10  includes base stations  12 , relay nodes  14  and mobile stations  16 . Base stations  12  communicate with one another and with external networks, such as the Internet (not shown), via carrier network  18 . Base stations  12  engage in wireless communication with relay nodes  14  and/or mobile stations  16 . Similarly, mobile stations  16  engage in wireless communication with relay nodes  14  and/or base stations  12 . 
     Base station  12  can be any base station arranged to wirelessly communicate with relay nodes  14  and/or mobile stations  16 . Base stations  12  include the hardware and software used to implement the functions described herein to support the MAC control plane functions. Base stations  12  include a central processing unit, transmitter, receiver, I/O devices and storage such as volatile and nonvolatile memory as may be needed to implement the functions described herein. 
     Mobile stations  16  can be any mobile station including but not limited to a computing device equipped for wireless communication, cell phone, wireless personal digital assistant (“PDA”) and the like. Mobile stations  16  also include the hardware and software suitable to support the MAC control plane functions needed to engage in wireless communication with base station  12  either directly or via a relay node  14 . Such hardware can include a receiver, transmitter, central processing unit, storage in the form of volatile and nonvolatile memory, input/output devices, etc. 
     Relay node  14  is used to facilitate wireless communication between mobile station and base station  12  in the uplink (mobile station  16  to base station  12 ) and/or the downlink (base station  12  to mobile station  16 ). A relay node  14  configured in accordance with the principles of the present invention includes a central processing unit, storage in the form of volatile and/or nonvolatile memory, transmitter, receiver, input/output devices and the like. Relay node  14  also includes software to implement the MAC control plane functions described herein. Of note, the arrangement shown in  FIG. 1  is general in nature and specific communication embodiments constructed in accordance with the principles of the present invention are described with reference to  FIGS. 2-6  below. Of note, according to an embodiment, base stations  12  and relay nodes  14  implemented in accordance with the principles of the present invention are fixed, i.e. non-moving devices, but the invention is not limited to such. It is contemplated that these devices may move. Mobile stations  16  can be fixed, stationary or moving. 
       FIGS. 2-6  are diagrams showing five different exemplary operational embodiments for base stations  12 , relay nodes  14  and mobile stations  16  in accordance with the principles of the present invention. It is noted that carrier network  18  is not shown in  FIGS. 2-6  to simplify explanation of the operating embodiments. 
       FIG. 2  is a diagram showing unbalanced relay operation. As is shown in  FIG. 2 , mobile station  16  communicates with base station  12  via relay node  14  in the uplink direction only. Base station  12  communicates in the downlink direction directly with mobile station  16 . Base station  12  is also shown as engaging in bi-directional communication with relay node  14  so that base station  12  can receive data from mobile station  16  via relay node  14  and engage in MAC control plane communications with relay node  14 . The unbalanced relay arrangement shown in  FIG. 2  relieves mobile station  16  from concerns over the peak to average power ratio (“PAPR”) and reduces the imbalance in the downlink (“DL”)/uplink (“UL”) link budget. Such occurs, for example, because the base station  12  is capable of much higher power transmission and is much more sensitive on the receiving side than mobile station  16  for wireless communications such as orthogonal frequency division multiplexed (“OFDM”) communications. In other words, within a given area supported by base station  12 , using an unbalanced communication arrangement such as that shown in  FIG. 2  allows a more even transmission power arrangement on the uplink and downlink because mobile station  16  can communicate with relay node  14  in the UL direction, which is presumably closer to mobile station  16  than base station  12  (at least for purposes of the present embodiment). In addition, the present arrangement as is shown in  FIG. 2  does not require any implementation or programmatic software changes or enhancements to mobile station  16  or base station  12  with respect to downlink communication because such is accomplished directly between base station  12  and mobile stations  16  as is known in the art. 
     In the uplink direction, base station  12  schedules uplink transmission for mobile station  16  and relay node  14 . Mobile station  16  makes its uplink transmission which is received and decoded by relay node  14 . Relay node  14  relays the traffic to base station  12 . Instead of ranging to base station  12 , mobile station  16  ranges to relay node  14 . As used herein, the term “ranging” is used as understood by one of ordinary skill in the art. “Ranging” refers to the process used in OFDM wireless communications to adjust the arrival time for different mobile stations  16  communicating with a single base station  12 . The ranging process is also used to establish the transmit power for mobile station  16 . The ranging process is analogous to a “handshake” between mobile station  16  and its communication partner, i.e. relay node  14 , in the uplink direction. The inclusion of relay node  14  in the embodiment shown in  FIG. 2  is transparent to mobile station  16 . In other words, because DL communication comes from base station  12  and not relay node  14 , mobile station does not know that its UL communication is not directly with base station  12  and is instead with relay node  14 . This arrangement provides a suitable low-cost, fixed relay node implementation embodiment. With respect to MAC enhancement, no additional MAC capability, e.g., downlink re-fragmentation, scheduling, etc., is needed in this embodiment. 
     However, management messages relating to relay node  14  are used to support the functionality described in this embodiment and might include, for example, a relay node report message that allows a relay node to report ranging codes, channel quality index, channel and downlink hybrid automated repeat request (“HARQ”) error control method acknowledgement channels and combined uplink traffic HARQ status messages for multiple mobile stations  16 . Another MAC management message may include a message sent by base station  12  to relay node (“RN”)  14  which enables base station  12  to indicate the uplink connection identification numbers supporting communication sessions. 
     A second operational embodiment of the present invention is described with reference to  FIG. 3 .  FIG. 3  shows a coverage hole  20  formed by non-overlapping coverage regions  22  supported by corresponding base stations  12 . In other words, each base station  12  supports a coverage region  22  for communication with devices in the corresponding coverage region  22 . However, there are situations in which coverage areas  22  may not overlap, thereby forming a “coverage hole”  20 .  FIG. 3  shows mobile station  16  positioned within coverage hole  20 . In such case, absent a solution, mobile station  16  would lose wireless communication with base stations  12 . In other words, a mobile station  16  at the edge of a coverage region  22 , i.e., cell is unable to decode broadcast control messages transmitted by any of base stations  12 . In this case, relay node  14  and its corresponding relay node coverage area  24  provides coverage within coverage hole  20 , thereby effectively eliminating the coverage hole and allowing a mobile station  16  in coverage hole  20  to wirelessly communicate with one or more base stations  12 . Note, although  FIG. 3  shows circular coverage in some areas  22 , the present invention is not limited to such. Coverage zones  22  shown in various shapes in the drawing figures purely for ease of explanation and understanding, it being recognized that coverage areas  22  can take the form of different shapes depending on the configuration of the antennas within each base station  12 . 
     In the case of the operational embodiment shown in  FIG. 3 , relay node  14  operates much like a base station  12  in that it relays all DL broadcast messages to mobile station  16  and relays all DL and UL unicast messages and traffic between mobile station  16  and base station  12 . Relay node  14  also manages the ranging operation with respect to its supported mobile stations  16 , conducts data scheduling and creates local map messages. Of note, the operation of mobile station  16  is not transparent because base station  12  is transmitting in the downlink to a relay node  14 . As such, transmissions to relay node  14  at the MAC layer may be re-fragmented for transmission to base station  12 . The data plane aspects of the MAC enhancement are referred to herein as “R-MAC”. As is discussed below in detail, a set of messages for communication between relay node  14  and base station  12  to support MAC control plane functions are implemented in accordance with the present invention. 
     A third operational embodiment is described with reference to  FIG. 4 . The embodiment shown in  FIG. 4  is used to enhance throughput within a coverage region  22 , i.e., cell. In this case, mobile station  16  at the edge of coverage region  22  is able decode broadcast control messages from base station  12 . However, because mobile station  16  is at the edge of the coverage region  22 , its capacity for communication with base station  12  is severely attenuated due to the low signal strength resulting from the distance from base station  12 . 
     In this embodiment, as noted above, mobile station  16  receives broadcast control messages from base station  12 . Relay node  14  relays only DL and UL unicast messages and traffic to/from mobile station  14 . In this case, relay node  14  performs data scheduling and downlink re-fragmentation. Accordingly, as with the previous embodiment ( FIG. 3 ), MAC control plane protocol is enhanced to provide a relay node MAC control plane enhancement (“R-MAC”) to support this refragmentation. 
     With respect to the operation of mobile station  16 , operation by mobile station  16  is not transparent because mobile station  16  may support the R-MAC control plane functions. In addition, a type interference control of relay node  14  is used so that communications to/from mobile station  16  can properly be supported. 
     The fourth operational embodiment is described with reference to  FIG. 5 . In the embodiment shown in  FIG. 5 , coverage is extended to mobile station  16  beyond the coverage area  22  of base station  12 . Relay nodes  14  are arranged to have overlapping relay coverage nodes area  24 . In this arrangement, relay nodes  14  include the full set of operational functions provided by a base station  12  plus the R-MAC layer. In addition, connection identification information for particular communication sessions as well as the implementation of the privacy functions are provided on an end-to-end basis, i.e. from mobile stations  16  to base station  12 . Relay node  14  also supports local DL channel description (“DCD”), UL channel description (“UCD”), mobile neighboring advertisement (“MOB_NBR_AVD”) messages, and the like. DCD messages provide downlink channel configuration information, such as power and timing adjustment rules. UCD messages include, for example, ranging code division information. MOB_NBR_AVD messages provide information relating to neighboring cells, HO information, etc. Relay node  14  also supports the information needed to route the mobile  16  station connection through the series of relay nodes  14  for communication with base station  12 . 
     As with the previous two embodiments, the operation of mobile station  16  includes the new R-MAC layer. This embodiment also implements an independent data transmit and receive schedule. Further, in accordance with the present embodiment, interference control of relay nodes  14  is not significant because the mobile station  16  only communicates with a relay node  14  (as to compared to both a relay node  14  and base station  12  in some capacity or form). 
     A fifth exemplary operational scenario is described with reference to  FIG. 6 . The embodiment shown in  FIG. 6  can be used to boost system capacity for a wireless communication transmission technology different than that supported by base station  12 . For example, the embodiment shown in  FIG. 6  shows code division multiple access (“CDMA”) wireless communication between relay node  14  and mobile station  16  but uses multiple input, multiple output (“MIMO”) OFDM wireless communication between base station  12  and relay node  14 . Multiple Input, Multiple Output Orthogonal Frequency Division Multiplexing (“MIMO-OFDM”) is an OFDM technology that uses multiple antennas to transmit and receive radio signals. MIMO-OFDM allows service providers to deploy wireless broadband systems that take advantage of the multi-path properties of environments using base station antennas that do not necessarily have line of sight communications with the mobile station. 
     MIMO systems use multiple antennas to simultaneously transmit data to the receiver, which processes the separate data transmissions. This process, called spatial multiplexing, can be used to proportionally boost the data-transmission speed by a factor equal to the number of transmitting antennas. In addition, since all data is transmitted both in the same frequency band and with separate spatial signatures, this technique utilizes spectrum very efficiently. The result is that CDMA system capacity is enhanced without actually impacting or requiring the upgrade of CDMA base stations and/or requiring the deployment of OFDM-based mobile stations  16 . 
     Under the architecture shown in the embodiment of  FIG. 6 , cell-wise backhaul is provided. Using a technology such as MIMO-OFDM for communication between base station  12  and relay node  14  allows the benefit of MIMO-OFDM transmission to be maximized. It is contemplated that such an arrangement can be provided by implementing MIMO-OFDM and CDMA at the physical layer within relay node  14 . As such, mobile station  16  and its use of CDMA is transparent to mobile station  16 . In other words, the embodiment shown in  FIG. 6  allows relay node  14  to act as a base station for the CDMA system. Although the embodiment shown in  FIG. 6  shows CDMA and MIMO-OFDM technologies, the general proposition of the embodiment in  FIG. 6  is that relay node  14  can provide an air interface translation function. In other words, the present invention is not limited solely to CDMA to MIMO-OFDM translation. 
     Of note, the operational embodiments shown in  FIGS. 2-6  as well as other drawing figures herein showing relay node  14  are not limited solely to the use of a particular piece of hardware. It is contemplated that mobile stations themselves can serve as relay nodes within the context of the present invention provided that mobile stations  16  are equipped with the software to implement the relay node functions described herein. In other words, a mobile station can serve as a relay node  14  provided that it is equipped with software supporting relay node functions. 
     In accordance with the present invention, a number of functions are defined to support the aforementioned operational embodiments. These MAC layer control functions provide the ability for mobile station  16  to enter and operate within a relay-based network. These functions include ranging, initial network entry for mobile station  16  and defining a frame structure for wireless communication between and among mobile station  16 , base station  12 , and relay node  14 . These functions also include the establishment of broadcast/unicast data/message transmission, and scheduling signaling. In addition, MAC layer control functions are provided for fast access point (“AP”) switching, relay node-related MAC management messages and sleep/idle mode operation. Each of these functions are described herein. 
     Ranging 
     As an initial matter, it is noted that the implementation of the ranging function for the embodiments shown in  FIGS. 2 ,  3 ,  5 , and  6  are the same as is currently known in the art, e.g., the same as in the IEEE 802.16d and e standards. However, current standards do not provide or propose support for the operational embodiment shown  FIG. 4  (system capacity enhancement through the use of relay nodes  14 ). A ranging design for that operational embodiment is described herein. In accordance with the present invention, there are two options for supporting ranging for the capacity enhancement embodiment ( FIG. 4 ). As a first option, three types of ranging regions can be defined, resulting in shorter delay to establish ranging, but high complexity with respect to the relay node  14  ranging process. As a second option, two types of ranging regions can be defined, resulting in a long ranging establishment delay but low complexity with respect to the relay node  14  ranging process. 
     Regarding the first option, the three ranging regions include a common initial ranging region for the first step initial ranging of network entry or re-entry, a common AP switch ranging region and a private ranging region. For the common initial ranging region, all of the access points in the cell, i.e., the base station  12  and all relay nodes  14 , monitor this region. The region may appear every N frames and is described in base station  12 &#39;s UL-MAP. With respect to code set division, the code set is divided to enable mobile stations  16  to indicate the preferred access point. The code set for the common initial ranging region is divided among all access points in a cell. Mobile station  16  sends a code selected within the domain of the relay node  14  if the mobile station  16  selects a particular relay node  14  as its access point. The second type of ranging region within this first option is the establishment of a common access point switch ranging region. All of the access points in a cell monitor this region, and the region may appear ever N frames and is described in base station  12 &#39;s UL-MAP. The code set is divided to enable base station  12  to ultimately indicate the access point, and each access point is allocated a code domain. To enable mobile  16  to use the dedicated code for the first step of AP switch ranging, the base station  12  or parent relay node  14  reserves a set of codes as temporary access point switch codes for intra-base station  12  access point switching. This arrangement speeds up the AP switching procedure. Mobile station  14  uses the temporary access point switch code on the common AP switch ranging region. Mobile station  14  uses the code selected within the domain of a selected relay node  14  between the common AP switch ranging region. 
     Finally, the private ranging region of the first option is described. In this region, each relay node and base station has its own private ranging region used for the second step of the initial ranging process and the second step of the AP switch ranging process. The second step means that after the first step of ranging process described above, the power and timing are aligned with the requirements of the access point. Private ranging region also allows for bandwidth request ranging and periodical ranging as well. The private ranging region is only monitored by relay nodes  14 . With respect to code set division, relay node  14  reserves a code set for the second step ranging whether for AP switching or initial ranging. The remaining codes are divided as bandwidth request codes and periodic ranging codes. The length of the code may be shorter than those used for base stations  12 , e.g., 74 versus 144 bits, since the interference within the region of a relay node  14  is less than compared with the base station because a smaller group of mobile stations  16  are supported by a relay node  14 . 
     With respect to the second option, the common initial ranging and common AP switch regions are combined as a single region. Under this option, the access point will not be able to determine the purpose of the ranging, i.e. inter-base station access point switching or initial ranging based on the code. Accordingly, a MAC header is defined so that the access point can poll mobile station  16  to determine the purpose of the ranging. Under the second option, a private ranging region is also established and is the same as that described above with respect to the first option. 
     With respect to both option 1 and option 2, it is contemplated that the available codes, e.g., 250 different codes, are arranged in a block in which different groups of codes are assigned to the different domains. For example, with respect to the common initial ranging region described with respect to option 1, it is contemplated that the block of 250 codes can be divided so that there is a domain for base station  12 , and a separate domain for each relay node  14  within the cell. With respect to the common switch ranging region for options 1 and 2, the block can be divided and a domain group reserved for intra-base station  12  switching and a separate group of codes assigned to establish domains for the various relay nodes within the group of common access points for inter-base station switching. Similarly, with respect to the private ranging region, the block of available codes can be divided into a second step ranging group domain, a periodic request domain, and a bandwidth request domain. Of note, with respect to the private ranging region, a shorter code length means a shorter ranging opportunity which means a smaller defined ranging region. Of note, for ranging purposes, the MAC header described above for option 2 can be added as an additional type in the feedback MAC header. The general concept of a feedback MAC header is known. However, the implementation of a ranging purpose function within that header is provided in accordance with the present invention. 
     Mobile Station Initial Network Entry 
     The present invention defines functions and procedures for allowing network entry of a mobile station  16  to a network having relay nodes  14 . Initial network entry relates to the selection of codes, such as OFDMA codes, from the UL-MAP and DL-MAP by mobile station  16 . Mobile station  16  selects a code base and tells base station  12  (or relay node  14 ) that mobile station  16  is going to join the network. In this case, base station  12  and/or relay node  14  monitor the ranging region, described above, to facilitate initial network entry of mobile station  16 . 
     An exemplary arrangement for the operational embodiments shown in  FIGS. 2 and 4  are described first. As an initial matter, it is presumed that all mobile stations  16  in this exemplary arrangement are able to decode broadcast control messages transmitted by base station  12 . In these embodiments, mobile station  16  enters the network through base station  12 . A common initial ranging region is dedicated for initial ranging, i.e., the common ranging region is used for the first step of initial ranging. The common ranging region is described in an uplink channel description (“UCD”) and/or UL-MAP message. Base station  12  and all relay nodes  14  within the coverage region  22  monitor this ranging region constantly in order to speed up initial network entry. As discussed above, the available codes are divided among base station  12  and relay nodes  14  within the same coverage region  22 , i.e., within the same cell. Base station  12  or relay node  14  is associated with the code set used by mobile station  16  to indicate its preferred access point in the first step of initial ranging. For example, these codes can be generated using the cell&#39;s uplink ID which can be a 7-bit field. 
     The method for selecting base station  12  is the same as is presently known in the art with respect to the initial network entry of a mobile station  16 . Downlink channel description (“DCD”) and UCD synchronization is performed by having mobile station  16  monitor DCD messages transmitted by base station  12 . However, base station  12  adds information related to relay node  14  such as a preamble index, transmit region, etc., to the DCD message. Similarly, mobile station  16  monitors the UCD messages transmitted by base station  12 . In this case, base station  12  adds relay information such as the code set corresponding to the relay node  14  for the first step of initial ranging, the ranging region, the number of hops (relay node  14  hops) to base station  12  as well an uplink relay identification number. Of note, the uplink ID for relay node  14  and the cell ID for the uplink are typically planned in advance and pre-assigned. 
     The operational embodiments shown in  FIGS. 2 and 4  also involve the selection of an access point, e.g., base station  12  or relay node  14 . In accordance with the present invention, mobile station  16  is arranged to detect relay preambles based on the general quantity measurement and number of hops. In accordance with the measurement and number of hops, the top 3 candidate access points are selected. 
     Mobile station  16  monitors the DL-MAP and UL-MAP to understand the common initial ranging region. Mobile station  16  selects a ranging code from the code set associated with the selected access point as was sent in the common initial ranging region. All relay nodes  14  and the base station  12  within coverage region  22  monitor the common initial ranging region and any relay node  14  which detected the code transmission informs base station  12  in the form of the received code index and signal strength. Base station  12  assigns a dedicated code for the second set of initial ranging as well time/power adjustment data. Base station  12  determines the access point for mobile station  16  based on (1) the code index received from mobile station  16 , i.e., the intended access point from the perspective of mobile station  16 , and (2) the load on the relay node  14  selected by mobile station  16 . 
     The second step of initial ranging is done in connection with the selected relay node  14 . In this case, base station  12  sends a ranging response message (“RNG-RSP”) which (1) accepts the access point selected by mobile station  16  or suggests another access point, (2) assigns the CID, and (3) includes any timing/power adjustments that may be used by mobile station  16  to facilitate the ranging process. Mobile station  16  then starts to monitor the transmit region corresponding to the selected relay node  14 . 
     The actual second step of initial ranging using the selected access point is the same as is known in the present art with the exception that the mobile station  16  has a dedicated code assigned for the second step of ranging after obtaining the relay transmit region. Of note, the above description of initial network entry for mobile station  16  with respect to the operational embodiment shown in  FIGS. 2 and 4  includes a generalized discussion of the process flow and dynamics among mobile station  16 , relay node  14  and base station  12 . The process flow for initial network entry for mobile station  16  is described from the point of view of mobile station  16  in  FIG. 7 , from the point of view of relay node  14  in  FIG. 8  and from the point of view of base station  12  in  FIG. 9  for the operational embodiments shown in  FIGS. 2 and 4 . 
     Referring to  FIG. 7 , with respect to mobile station  16 , mobile station  16  selects the cell, i.e. coverage region  22  it wishes to communicate within (Step S 100 ). Mobile station  16  synchronizes the DCD message as described above (Step S 102 ). The preferred access point is selected by mobile station  16  (Step S 104 ) and transmitted to base station  12  and sends this as part of the first step initial ranging code (Step S 106 ). Mobile station  16  then waits for the RNG-RSP from base station  12  (Step S 108 ). 
     When mobile station  16  receives the RNG-RSP from base station  12  (Step S 110 ), mobile station  16  engages in second step initial ranging with the selected access point using a dedicated code (Step  112 ). Recall that the RNG-RSP received from base station  12  includes the access point selected by base station  12 . 
     If, during Step S 108 , the RNG-RSP is not received and a predetermined timer (“T 1 ”) expires (Step S 114 ), the first step initial ranging code is re-sent a predetermined number of times until its retry quantity is exhausted (Step S 116 ). Once the retry quantity is exhausted, mobile station  16  begins the network re-entry process again (Step S 118 ). 
     Turning now to  FIG. 8 , relay node  14  monitors the common initial ranging region (Step S 120 ) until a code transmission is detected (Step S 122 ). When a code transmission is detected, relay node  14  evaluates the code to determine whether mobile station  16  selected a code corresponding to that relay node  14  (Step S 124 ). If the code transmission does not indicate that the particular relay node  14  has been selected, the assigned code is released by relay node  14  (S- 126 ). If relay node  14  was selected, a “code_grab” message is sent to base station  12  (Step S 128 ) indicating that the mobile station  16  selected the particular relay node  14 . Relay node  14  decodes the RNG-RSP message sent from base station  12  to mobile station  16  (in other words, it detects the RNG-RSP message as well) or receives a separate MAC layer message from base station  12 . Relay node  14  evaluates the message to determine whether a CID has been assigned to mobile station  16  (Step S 132 ). If a CID has not been assigned, relay node  14  releases the assigned code. If a CID has been assigned, relay node  14  monitors the assigned code transmission on its own private ranging region for the subsequent ranging process, i.e. the second step initial ranging (Step S 134 ). 
     Referring to  FIG. 9 , base station  12  initially transmits the DCD/UCD messages to be synchronized by mobile station  16  (Step S 136 ). At this point, base station  12  monitors the common initial ranging region (Step S 138 ) for the detection of a code transmission by mobile station  16  (Step S 140 ). After Step S 136 , base station  12  also waits for the “code_grab” message from relay nodes  14  (Step S 142 ). If a “code_grab” message has been received (Step S 144 ) and base station  12  detects that a code has been transmitted (Step S 140 ), base station  12  evaluates the transmission and “code_grab” message to determine the access code corresponding to mobile station  16  that transmitted the code to base station  12 . Base station  12  then sends the above-described RNG-RSP or other MAC control layer to the relay node  14  (Step S 148 ). 
     Also consider the example where there are two relay nodes  14 , namely relay A and relay B. In terms of signaling exchange, base station  12  transmits the DCD (in its coverage region  22 ), UCD, DL-MAP, UL-MAP to mobile station  16 . Now, consider that mobile station  16  selects relay B. Mobile station  16  transmits the code corresponding to relay B on the common initial ranging region. This code is received by relay A, relay B and base station  12 . Relay B then transmits a “code_grab” message which is received by base station  12 . Base station  12  transmits the RNG-RSP message to mobile station  16 . Relay B then transmits its DL-MAP and UL-MAP for relay B. Mobile station  16  transmits the ranging code assigned by relay B and relay B then transmits a RNG-RSP message, adjusting power and time alignment. 
     The previous description was, as noted, for the operational embodiments shown in  FIGS. 2 and 4 . The initial network entry process for the operational embodiment shown in  FIGS. 3 and 5  is now described. In these operational embodiments, mobile station  16  enters the network through a relay node  14 . This process can be the same as is currently known, with the exception that mobile station  16  detects the selected relay nodes  14  transmit region by detecting forward channel information at the physical layer. Access point selection for these operational embodiments is known, and is the same as current design-preamble detection with the addition that the relay node  14  preamble is defined. In accordance with the operational embodiment shown in  FIGS. 3 and 5 , mobile station  16  searches for an R-MAP (MAP corresponding to the relay node  14 ) through the relay forward channel at the physical layer (“R-FCH”). As with the previously described operational embodiment initial network entry process, mobile station  16  synchronizes DCD and UCD by monitoring DCD from the relay node  14 . Of note, although mention is made that the initial network entry process for the operational embodiments in  FIGS. 3 and 5  is similar to that currently known, it is contemplated that the present invention is not so limited and that variations can be supported as the current standards are further developed. 
     Frame Structures 
     In accordance with the present invention, logical frame structures are defined and implemented in various scenarios to establish the extent to which a mobile station  16  can wirelessly communicate with base station  12  or the extent to which mobile station  16  wirelessly communicates via relay node  14 . In each case, the logical frame structure that is implemented to communicate using relay node  14  is divided into a base station downlink sub-frame and a base station uplink sub-frame in terms of timing. In certain embodiments, the DL sub-frame and the UL sub-frame allocate a portion of the sub-frame for communication with relay node  14 . 
     In the first scenario, all mobile stations  16  within coverage region  22  can receive transmissions from base station  12 . This arrangement involves base station  12  allocating a burst in the UL sub-frame to enable relay node  14  to unicast uplink traffic and to indicate to base station  12  the detection of ranging code transmission. In other words, in this scenario, the base station DL sub-frame is unchanged from that currently used with the exception that the control message transmitted by the base station in the DL sub-frame is received by mobile station  16  and relay node  14 . However, unlike currently proposed standards, a portion of the base station  12  UL sub-frame is dedicated to allowing relay node  14  to transmit to base station  12  based on the burst allocated in the UL-MAP. In other words, there is a mobile station  16  unicast message/traffic/ranging indicating component of the base station UL sub-frame transmitted by relay node  14  and received by base station  12  and mobile station  16 . 
     In the second scenario, some mobile stations  16  within coverage area  22  cannot receive traffic from the corresponding base station  12 . In this arrangement, R-FCH is used to indicate the burst location and physical parameters of the R-MAP. R-MAP is used for relay node  14  resource allocation signaling and includes information elements (“IE”) supplying the same. The frame structure for this scenario includes a preamble used for mobile station  16  access to relay node  14 . Of note, the frame structures described herein are with respect to and from the point of view of relay node  14 . 
     In this scenario, the base station DL sub-frame, in addition to the preamble and DL-MAP and UL-MAP, includes a portion in which relay node  14  transmits a broadcast control message, unicast message and/or traffic that is received by mobile station  16 . This carved out portion of the base station DL sub-frame also includes the above-described R-MAP. In the base station UL sub-frame portion of the frame, that is received by relay node  14  from mobile stations  14 , there is a portion used for initial ranging that includes information elements from the R-MAP. In addition, the base station UL sub-frame includes a portion transmitted by relay node  14  to base station  12  based on the burst allocated in the UL-MAP. In other words, the base station UL sub-frame includes a portion which is used by mobile stations  16  to transmit to relay node  14  and a portion used by relay nodes  14  to transmit to base stations  12 . 
     In the third scenario, all mobile stations  16  within coverage area  22  can receive from base station  12 . However, unlike scenario one described above, the third scenario provides for handoff and includes a common initial ranging region and common handoff (“HO”) ranging region. This scenario is described with reference to the logical frame structure shown in  FIG. 10 . Frame  26  includes base station DL sub-frame  28  and base station UL sub-frame  30 . Base station sub-frame  28  includes relay node receive portion  32  and relay node transmit portion  34 . Relay node receive portion  32  is received from base station  12  and relay node transmit portion  34  is transmitted to mobile stations  16  within the cover zone  24  of relay node  14 . Relay node receive portion  32  itself is further divided into preamble for base stations  12  and relay nodes  14  in the form of preamble  36 . Of note, preamble  36  can include the same or different preambles corresponding to base station  12  and relay nodes  14 . DL-MAP and UL-MAP portion  38  of relay node receive portion  32  include information elements corresponding to a common handoff (“HO”) ranging and common initial ranging codes. Finally, relay node receive portion  32  includes a base station transmit section  40  which includes traffic, control and messaging information transmitted by base station  12  and is received by relay nodes  14  and mobile stations  16 . 
     Relay node transmit portion  34  is received by mobile stations  14  within relay node coverage zone  24  and includes R-MAP  42  and unicast message/traffic section  44 . R-MAP  42  includes information elements which are used to indicate the relay node private ranging region. 
     Base station UL sub-frame  30  includes relay node receive portion  46  and relay node transmit portion  48 . However, unlike the base station downlink sub-frame, relay node receive portion  46  is received by relay nodes  14  from mobile stations  16  and relay node transmit portion  48  is transmitted to base station  12  based on the burst allocated in the UL-MAP. Relay node receive portion  46  includes uplink mobile station transmit portion  50  which is received by relay node  14  and base station  12  that includes traffic, and other message information. Relay node receive portion  46  also includes common initial ranging region  52 , common HO ranging region  54  and receive node private ranging region  56 . Common initial ranging region  52  is, as discussed above, used by mobile station  16  for first step initial ranging in which base station  12  controls the resource allocation for the initial ranging region. Common HO ranging region  54  is used for the first step access point switch ranging in which the base station  12  controls the resource allocation for the AP switch ranging region. Relay node private ranging region  56  is used for mobile station  16  ranging to relay node  14  in which relay node  14  controls the resource allocation for dedicated ranging region for the mobile station  16 . Of note, R-FCH is used to indicate the burst location and physical parameters of the R-MAP. 
     In the fourth scenario, not all mobile stations within a coverage area  22  can receive from base station  12  and some relay nodes  14  likewise cannot receive from base station  12 . The resulting frame structure is for a first hop relay in which other relays rely on the first hop relay node  14  for access to base station  12 . This scenario is similar to the second scenario described above. However, in this scenario, the base station DL sub-frame relay node receive portion includes downlink base station transmit data that is received by the first hop relay node  14  and mobile stations  16 . Further, the downlink relay node portion of the DL sub-frame is transmitted to other second hop relay nodes  14  in addition to mobile stations  16 . 
     On the base station UL sub-frame portion of the overall frame, the initial ranging region is received from mobile station  16  and other second and higher hop relay nodes  14 . 
     Data/Message Transmission and Scheduling Signaling 
     The present invention provides MAC control plane arrangements for broadcast control message transmission. In accordance therewith, it is contemplated that the present invention supports global broadcast control messages from the perspective of base station  12 . As noted above, these broadcast control messages include the DL-MAP and UL-MAP, DCD and UCD messages as well as any other messages that can be broadcast by base station  12 . In general, relay node  14  relays global broadcast messages originally transmitted by base station  12  if there is at least one mobile station  16  which has entered the network through that same relay node  14  and also indicates its intention of needing relay node  14  to relay the global broadcast control messages. This intention can be made by mobile station  16  transmitting a control plane message to relay node  14 . In addition, relay node  14  can relay global broadcast messages if the relay node  14  has sufficient resources to do so, e.g., it can do so without causing additional channel interference. 
     It is also contemplated that relay node  14  can itself broadcast local broadcast control messages. Such can be accomplished by a message which includes a relay node  14  local burst profile as well as a channel that has been defined for such relay node  14  local broadcast control. Such local broadcast control messages can also include a local neighborhood advertisement by relay node  14  if at least one mobile station  16  needs the global control message relayed. In other words, local broadcast control messages can be used by relay node  14  to relay global broadcast control messages transmitted by base station  12 . 
     Downlink traffic transmission is explained to  FIG. 11 .  FIG. 11  shows three examples of downlink traffic transmission block diagrams. With respect to downlink resource allocation signaling, both base station  12  and relay nodes  14  use a MAP to transmit data scheduling signaling. In addition, relay nodes  14  broadcast their own scheduling information through their own MAP, defined and described herein as R-MAP. Relay nodes  14  receive data from their corresponding parent nodes, whether base station  12 , or, in the case of multi-hop relay nodes, another relay node  14 . Mobile stations  12  are permitted to receive downlink data from a relay node  14  and base station  12  if possible, based for example, on the difference in signal strength between relay node  14  and base station  12  being larger than a predetermined amount. It is contemplated that the routing table can be a CID-based design as is known in the art. 
     Channel quality indication (“CQI”) feedback is also contemplated. CQI is used by relay nodes  14  and base stations  12  based on feedback received from mobile station  16  to establish channel parameters such as power level, etc. In this case, mobile station  16  feeds back the CQI corresponding to relay node  14  in a time division multiple access (“TDMA”) or CDMA fashion to its access point. The access point may relay the CQI of further up the signal chain, i.e. to base station  12  and relay nodes  14  closer to the base station  12 . 
     Referring to  FIG. 11 , downlink traffic transmission arrangement  58  includes relay node burst  60 . In the case of arrangement  58 , data burst  62  is transmitted by base station  12  (it is shown in downlink frame  64  outside of the relay node burst  60  area). Download traffic transmission arrangement  66  shows a frame structure in which a data burst  62  is transmitted by base station  12  and a data burst  62  is transmitted by relay node  14  within relay burst  60 . Finally, arrangement  68  shows data burst  62  transmitted on the uplink by relay node  14  as part of the relay node burst  60 . In sum, downlink traffic transmission and the corresponding data burst  62  can be done by one or both of base station  12  and relay node  14 . Of note, each of arrangements  58 ,  66  and  68  shows CQI  70  transmitted by mobile station  14  on the uplink portion of the frame. 
     Uplink traffic transmission uses UL resource allocation signaling in which both base stations  12  and relay node  14  use a MAP, previously described, to transmit allocation signaling. UL unicast traffic from mobile station  16  is monitored by its access point. Further, UL traffic from relay node  14  (to base station  12  or another relay node  14 ) is monitored by that parent access point. It is contemplated that a control plane message can be used by relay node  14  and sent to mobile station  16  to inform mobile station  16  of uplink resource assignments. 
     Fast Access Point Switching 
     Fast access point (“AP”) switching is used to minimize handoff delay as a mobile station  16  switches from access point to access point, i.e. from relay node  14  to another relay node  14 , corresponding to the same or different base stations  12 . A macro diversity set is established by mobile station  16  based on measurements, e.g., general quality measurements, taken by mobile station  16 . Mobile station  16  establishes the members as potential handoff candidates. Members in the macro diversity set share information regarding switching. The arrangements described herein are suitable for all operational embodiments described above. The macro diversity set includes multiple nodes, e.g., relay nodes  14  and/or base stations  12 . In order to conserve resources, a predetermined maximum can be established. For example, an upper limit of 8 can be established as the maximum number of members in the macro diversity set. Of course, it is contemplated that the present invention is not limited to 8, and any number can be used subject to the processing and storage capabilities of base station  12 , relay node  14  and mobile station  16  within system  10 . 
     Regarding the macro diversity set, DL data is multicast at the base station  12  level, and not the relay node  14  level. For example, if all members are covered by two base stations  12 , downlink data is multicast only from those two base stations  12 . It is contemplated that the macro diversity set creation and update processes can be the same as is currently employed in a mobile station and base station environment, subject to further enhancement as may occur in the art. 
     The first example is shown in  FIG. 12  in which mobile station  16  is moving from a relay node coverage area  24  supported by a first relay node  14  into a second relay node coverage area  24  corresponding to a second relay node  14  within a single coverage region  22  supported by base station  12 . This example is suitable for all operational embodiments described above even though  FIG. 12  generally depicts the capacity enhancement example shown in  FIG. 4 . 
     In this first example, inter-relay node hand off ranging is a deterministic event. Each relay node  14  and the base station  12  reserve a predetermined quantity of handoff codes within the code set for intra-base station, e.g., handoff between relay nodes  14  within the coverage region  22  for a base station  12 . Although certainly not an absolute limitation, an exemplary limitation would reserve less than 3 handoff codes within the code set for intra base station handoff. 
     A temporary handoff code assigned by the first relay node is assigned to identify a mobile station  14  during handoff ranging to the second (target) relay node. The result is a short delay and a random handoff procedure is fully avoided. In accordance with this first example, it is not necessary to send an RNG-REQ, thereby resulting in lower overhead because the mobile station  14  is identified by the handoff code itself. In addition, no association is needed. Association refers to monitoring the target AP and communicating with the target AP even though mobile station  16  is still logically associated with the first AP. It is estimated that handoff duration can be accomplished within three to four frames using this example. As such, this first example is suitable for handoff by a mobile station  16  from base station  12  to relay node  14 , from a first relay node  14  to a second relay  14 , and from a relay node  14  to a base station  12 . Further, it is contemplated that this first example is suitable to facilitate handoff from a relay node  14  to a second relay node  14  corresponding to a same parent relay node  14 , from parent relay node to child relay node  14  and vice versa. As used herein, parent relay node  14  refers to a relay node that is closer in number of hops to base station  12 . 
     The intra-base station switching process is described with reference to  FIGS. 13-15  in which  FIG. 13  describes the switching from the perspective of mobile station  16 ,  FIG. 14  describes the intra base station switching from the perspective of the target (second) relay node  14 , and  FIG. 15  describes the switching process from the perspective of base station  12 . Referring first to  FIG. 13 , mobile station scans for potential access points to create a macro diversity set (Step S 150 ). Mobile station  16  sends the indication of its desired access point switch to its anchor node, i.e., the current relay node  14  or base station  12  serving mobile station  16  (Step S 152 ). Mobile station  16  receives the anchor switch information element (Step S 154 ) and sends the first step AP switch ranging code on the common AP ranging region (Step S 156 ). Mobile station  16  then waits for the RNG-RSP from the new AP (Step S 158 ). If the RNG-RSP is received from the new access point (Step S 160 ), then mobile station  16  performs second step access point switch ranging, i.e., sending the code on the access point&#39;s private ranging region and continues with operation (Step S 162 ). Steps S 164 , S 166  and S 168  are the same as those described above with respect to Steps S 114 , S 116  and S 118  in  FIG. 7  in the case where the RNG-RSP message is not received from the new access point. 
     With respect to the target relay node  14 , as is shown in  FIG. 14 , target relay node  14  waits for the AP switch indication from base station  12  or its parent relay node  14  (Step S 170 ). If and when the switch indication is received (Step S 172 ), the target access point monitors the assigned access point switch code on the common AP switch ranging region (Step S 174 ). When it detects its switch code (Step S 176 ), the target relay node  14  sends an RNG-RSP message to mobile station  16  and informs base station  12  that it has done so (Step S 178 ). Target relay node  14  then performs the ranging procedure on the private ranging region using the access point switch code dedicated to it (Step  180 ). If ranging is not successful, target relay node  14  again performs Step S 180 . If ranging is successful, target relay node  14  performs normal operation with respect to communications with other relay nodes  14 , mobile station  16  and base station  12  (Step S 184 ). 
     Referring to  FIG. 15 , from the perspective of base station  12 , base station  12  waits for relay node  14  to relay the access point switch request received from mobile station  16  (Step S 186 ). This is the case for those scenarios where mobile station  16  is not able to communicate with base station  12 . When the access point switch request is received by base station  12  (Step S 188 ), base station  12  sends an indication of the access point switch to the target relay node  14  (Step S 190 ). Base station  12  waits for “code_grab” message from the target relay node  14  (Step S 190 ). When the “code_grab” message is received (Step S 194 ), base station  12  releases the access point switch code temporarily assigned to the target relay node  16  so it can be re-used (Step  196 ). 
     The second example of access point switching is inter-base station switching. Under this example, inter-base station switching is equivalent to inter-parent relay node switching. The arrangement shown in  FIG. 16  is an exemplary diagram of inter-base station switching, it being understood that relay nodes  14  can take the place of base stations  12  in  FIG. 16 . This example, like the previous example, is suitable for all operational embodiments described above with respect to  FIGS. 2-6 . Referring to  FIG. 16 , inter-base station handoff is generally considered a random event if there was no inter-base station communication. Such is the case because mobile station  16  is moving from a region supported by one base station  12  into another base station  12  region. Mobile station  16  uses a handoff code selected from a code set associated with the selected target base station  12  (or relay node  14 ) for the first step handoff ranging on a common handoff ranging region. The target relay node  14  can then assign a dedicated handoff code for the mobile station  16  so that mobile station  16  can perform second step ranging in the target relay nodes ranging region. The remainder of the handoff procedure is known in the art and is not described herein. 
     Inter-base station switching processes from the perspective of the target relay node  14  and base station  12  are described with reference to  FIGS. 17 and 18 , respectively. The operation for inter-base station switching is the same as for intra-base station switching described above with respect to  FIG. 13 . Referring to  FIG. 17 , target relay node  14  monitors the common access point switch ranging region (Step S 198 ). When it detects its code transmission (Step  200 ), it sends an RNG-RSP message to mobile station  16  and informs its corresponding base station  12  (Step S 202 ). Target relay node  14  then performs a ranging procedure on the private ranging region using its dedicated AP switch code (Step S 204 ). The ranging procedure continues until mobile station  16  has successfully completed power and time alignment, i.e., the range of procedure is successful (Step S 206 ) at which point target relay node  14  engages in normal operation with respect to the mobile station  16  and base station  12  (Step S 208 ). 
     Referring to  FIG. 18 , the process flow for target base station  12  is described. Initially, base station  12  waits for target relay node  14  to relay the access point switch request from mobile station  16  (Step S 210 ). When the switch request is received (Step S 212 ) base station  12  determines whether it is the target of the handoff (Step S 214 ). In other words, base station  12  determines whether it is the target access point. If base station  12  is not the target, thereby implying that a relay node  14  within its coverage region  22  is the target, base station  12  sends an indication to the target relay node  14  that the target relay node is the access point switch (Step S 216 ). The target relay node  14  is also allocated a temporary switch access point switch code by base station  12 . Base station  12  waits to receive the “code_grab” message from the target relay node  14  (Step S 218 ). When the “code_grab” message is received (Step S 220 ), base station  12  releases the temporary access point switch code so it can be re-used (Step S 222 ). 
     If base station  12  is the target access point (Step S 214 ), it monitors the common access point switch ranging region (Step S 224 ). When base station  12  detects the first step access point switch ranging code (Step S 226 ), it sends an RNG-RSP message, assigning a dedicated AP switch code to mobile station  16  (Step S 228 ). Steps S 230 , S 232  and S 234  correspond to Steps  204 ,  206 , and  208  on  FIG. 17  regarding the private ranging procedure and the commencement of normal operation. 
     Flow control at the MAC control plane level is used to control multicast data transmitted from base station  12  to relay nodes  14  and base stations  12  to base station  12  (such as is used in handoff operation) to preserve communication channel resources. Flow control is implemented in accordance with the principles of the present invention between base stations  12  to facilitate smooth switching. Toward that end, relay nodes  14  maintain an upper bound for a communication data rate for each served mobile station  16  within relay node coverage area  24  of corresponding relay node  14 . This upper data rate bound can be set based on an average data rate for handover action time. Handover action time refers to the duration between the time mobile station  16  sends a handoff indication to the time mobile station  16  starts to monitor the new access point. 
     Flow control at the MAC control plane layer involves information exchange between base station  12  and relay node  14  or between parent relay node  14  and its child relay node  14 . In such cases, relay node  14  informs base station  12  or parent relay node of the average data rate. This can be in an absolute value. Relay node  14  can also include a stop command after receiving mobile station&#39;s  16  handover indication or the boundary of a data buffer is reached. A start command can be sent once buffer room is available. Relay node  14  can also transmit the average data rate change to inform the parent relay node or base station  12  to increase or decrease data transmission rate. This can be done based on buffer capacity. 
     It is also contemplated that base station  12  can control the downlink data for transmission rate to the mobile station  16  from a relay node  14  to minimize radio resource waste and to ensure that data week transmission is not necessary based on post-switch continuity. 
     MAC Control Plane Management Messages 
     In accordance with the present invention, a number of different type of MAC control layer management messages are provided to support wireless relay node communications. These messages include configuration, traffic scheduling, flow control, mobile station network entry, AP switching messages and a security key management message if relay node  14  implements a privacy, i.e. security, sub layer. 
     Regarding configuration, an “R-CD” message is provided for use in both the uplink and downlink directions between the relay node  14  and mobile station  16 . The R-CD message includes the identification of the relay node  14  (“R-ID”), the downlink channel ID, configuration change count, DL/UL burst profile as well as a number of type length values (“TLVs”) such as the bandwidth request code set domain, periodic ranging code domain, bandwidth request ranging backoff/end and periodic ranging start/end. 
     Regarding traffic scheduling, the R-MAP message is discussed above in detail. One or more IEs include the CID, burst description, i.e. duration, DIUC/UIUC, MIMO-related parameters and HARQ-related parameters. Regarding flow control, a flow control message (“R-FLW-CNTL”) is used to implement the flow control process described above. The R-FLW-CNTL message includes a number of basic CIDs, in which for each basic CID there is an indication of the absolute data rate or change step as noted above. 
     As noted above, relay node  14  can assist mobile station  16  with network entry. In accordance therewith, an “R_ranging_detection” message is defined for communication between relay node  14  and base station  12 . The “R_ranging_detection” message includes ranging code attributes of first step ranging and may also include time/power adjustment data and an assigned dedicated code for the second step ranging. The present invention also contemplates an “R_AP_switch” to facilitate and support AP switching when sent from the old (first) AP to base station  12 . The message includes the basic CID of mobile station  16  requesting the AP switching. When sent from the target (second) base station  12  to the old (first) base station  12 , the “R_AP_switch” message includes the assigned temporary code for the first step AP switch ranging. When sent from base station  12  to target relay node  14 , the “R_AP_switch” message includes the assigned code that the target relay node  14  needs to monitor. Further, an “R_ranging_detection” message for use between relay node  14  and base station  12  is used to provide the code detected on the common AP switch region. Of note, although particular names have been defined for the above-described messages, the present invention is not limited solely to the use of these names. Any name can be used to define these messages, it being understood that the data carried within the message is the relevant aspect. 
     Standards, such as the 802.11 standards already define certain MAC control plane management messages. In accordance with the present invention, these MAC management messages can be enhanced. For example, the DCD of base station  12  is enhanced such as for each relay node  14  in the coverage region  22 , DCD includes the R-ID, preamble index, transmission region, and uplink cell identification. The UCD of base station  12  is enhanced to include the common initial ranging region and code division and common AP switch region and code division as discussed herein. UL-MAP of base station  12  is enhanced to include the common AP switch region as discussed herein. The “MOB_scan_report” message for mobile station  16  is enhanced to include the preference of mobile station  16  regarding the access point from which it wishes to receive broadcast control messages. The “MOB_scan_report” can also include the signal strength. The “RNG-REQ” for relay node  14  is enhanced to include the R-ID of the relay node. Finally, the “anchor_switch” information element for relay node  14  includes the temporary code assigned by base station  12 . 
     Sleep/Idle Mode Operation 
     It is contemplated that the present invention supports a sleep/idle mode to conserve transmission resources and battery power. The sleep/idle mode is suitable for the operational embodiments shown in  FIGS. 2 and 4 . Of note, sleep/idle mode is meaningful only within a cell, i.e., coverage region  22 . In that regard, mobile station  16  monitors the base station  12  during a predefined listening/paging window. In such case, ranging is only done to base station  12  and an intra-base station switch does not trigger an access point switch in the case of sleep/idle mode operation. 
     The present invention advantageously provides and defines a comprehensive system and method for implementing MAC layer control plane functionality for wireless communication networks using stationary relay nodes. The present invention provides a set of functions and defines novel MAC control layer messages. 
     The present invention can be realized in hardware, software, or a combination of hardware and software. Any kind of computing system, or other apparatus adapted for carrying out the methods described herein, is suited to perform the functions described herein. 
     A typical combination of hardware and software could be a specialized or general purpose computer system having one or more processing elements and a computer program stored on a storage medium that, when loaded and executed, controls the computer system such that it carries out the methods described herein. The present invention can also be embedded in a computer program product, which comprises all the features enabling the implementation of the methods described herein, and which, when loaded in a computing system is able to carry out these methods. Storage medium refers to any volatile or non-volatile storage device. 
     Computer program or application in the present context means any expression, in any language, code or notation, of a set of instructions intended to cause a system having an information processing capability to perform a particular function either directly or after either or both of the following a) conversion to another language, code or notation; b) reproduction in a different material form. In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. Significantly, this invention can be embodied in other specific forms without departing from the spirit or essential attributes thereof, and accordingly, reference should be had to the following claims, rather than to the foregoing specification, as indicating the scope of the invention.

Metadata:
Filing Date: 20061110
Publication Date: 20140225
Grant Date: 20140225
Priority Date: 20051110
Inventors: ZHANG HANG
FONG MO-HAN
ZHU PEIYING
MA JIANGLEI
TONG WEN
Assignee: APPLE INC
CPC Classifications: [{"code": "H04B7/15507", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W48/08", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W48/08", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W84/047", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W16/26", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W84/047", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B7/15507", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W16/26", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 38022935