Abstract:
By using allocated spectrum from the mobile station air interface, one or more remote, child access points within a wireless communication network establish backhaul connections to a parent access point having conventional backhaul links to the network. In this manner, backhaul traffic is carried on the standard air interface coexistent with the normal mobile station traffic. Such an arrangement permits parent and child access points to use the standard air interface for both conventional mobile station traffic, as well as backhaul traffic. In an exemplary embodiment, a wireless cellular communication network establishes backhaul connections between one or more child Radio Base Stations (RBSs) and a parent RBS using one or more of the data channels defined by the network&#39;s air interface.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention generally relates to wireless communication networks, and particularly relates to carrying backhaul traffic on the in-band air interface utilized by such networks.  
           [0002]    Wireless communication networks generally include one or more Radio Access Networks (RANs) that provide access to the network. The RAN includes the transceiver resources and associated processing required for supporting radio communication with mobile stations, such as radiotelephones. A typical RAN includes a base station controller and a plurality of radio base stations (RBSs) that serve as access points (APs) for mobile stations. The base stations transmit communication traffic and control data to mobile stations on a forward radio link, and receive communication traffic and control signaling from the mobile stations on a reverse radio link. The frequencies, timing, structure, modulation, and other characteristics of such radio links are governed by the particular “air interface” adopted by the wireless network.  
           [0003]    The BSC supervises the operation of the base stations and interfaces the RAN with a core network (CN), which communicatively couples the RAN to the Public Switched Telephone Network (PSTN) and to external Packet Data Networks (PDNs), such as the Internet. The CN may include both circuit-switched and packet-switched communication entities supporting both circuit-switched and packet-switched communication traffic being carried to and from the mobile stations supported by the RAN.  
           [0004]    The radio base stations do not use the mobile station air interface for communication with the supporting BSC. Rather, such communication links, generally referred to as “backhaul” links, rely on relatively high bandwidth dedicated communication links, such as T1/E1 lines and/or microwave relay stations. The structure, synchronization, data formats, and signaling protocols differ significantly between the backhaul links and the air interface radio links. Incoming traffic from the core network destined for one or more mobile stations is reformatted for radio transmission according to the requirements of the air interface, and outgoing traffic received from the mobile stations is reformatted for transmission according to the protocol(s) established for the backhaul links.  
           [0005]    While dedicated backhaul links provide the bandwidth and reliability needed to carry the aggregate traffic and control signaling passing through the RAN, they impose potentially significant economic and physical barriers to the initial deployment of new wireless networks or the expansion of existing ones. Such barriers arise from, for example, the expense and difficultly of installing land-based backhaul communication links to each of the radio base stations in a RAN. As such radio base stations typically are arranged in a distributed “cellular” pattern, dedicated backhaul links must be installed for each cell.  
           [0006]    In poorer countries, such installation may not be practical because of cost constraints, or because the labor and materials necessary for such installation simply are lacking. Even where cost is not the overriding concern, the terrain may be too rugged, or the network operator may need to become operational more quickly than would be practical with land-line construction delays. While microwave links overcome some of the construction difficulties, microwave-based solutions still present technological difficulties, and do nothing to reduce expenses.  
           [0007]    Thus, the conventional approach to backhaul interconnection in wireless communication networks can, in some circumstances, unnecessarily delay network deployment and significantly increase the costs of such deployment. Under certain operational conditions, such as where one or more cells in the network are relatively lightly loaded, a different, lower cost backhaul interconnection might be adopted such that deployment costs and complexity are reduced.  
         BRIEF SUMMARY OF THE INVENTION  
         [0008]    The present invention comprises a method and apparatus for carrying backhaul traffic between radio access points in a wireless communication network using a portion of the air interface provided for supporting mobile station communications. In an exemplary embodiment, backhaul traffic, including mobile station and access point control signaling, passes between a “child” access point and a “parent” access point via the air interface on one or more of the air interface&#39;s data channels ordinarily used for carrying traffic to or from mobile stations. Such an arrangement permits the deployment of child access points without requiring the installation of conventional backhaul links to the child access points.  
           [0009]    In an exemplary embodiment, Radio Base Stations (RBSs) within a cellular network serve as the access points, and a parent RBS sends and receives backhaul traffic for one or more child RBSs using one or more communication channels defined by the network&#39;s air interface. Preferably, the parent RBS includes a relatively high bandwidth backhaul connection, such as leased T1/E1 lines or a microwave link. Thus, the parent RBS consolidates backhaul traffic received from child RBSs on the air interface for transport to other entities in the network over the conventional backhaul link, and distributes backhaul traffic received through its conventional backhaul link for the child RBSs to those child RBSs via transmission on the air interface. Essentially, one RBS transmits backhaul traffic to another RBS as would a mobile station transmit mobile station traffic.  
           [0010]    One exemplary embodiment uses simplex links between the parent RBS and a child RBS. With such an arrangement, the parent and child RBSs each have an associated “backhaul module” that may be thought of as a specially configured mobile station (e.g., cellular phone) that includes a directional backhaul antenna. The backhaul module at the parent RBS transmits forward backhaul traffic on the allocated air interface channel(s) via its high-gain antenna, and such transmissions are received by the child RBS(s) preferably on the child&#39;s primary antenna, i.e., the cell site&#39;s air interface antenna, used to support mobile station communications. Similarly, the backhaul module at the child RBS transmits reverse backhaul traffic to the parent RBS via its high-gain, directional backhaul antenna for receipt at the parent RBS via the parent&#39;s primary antenna.  
           [0011]    Use of the simplex links, among other things, avoids using any portion of the RBS&#39;s transmit power for backhaul traffic transmission, and provides the flexibility to assign the simplex links to use air interface spectrum in either the forward or reverse link allocations. That is, a given simplex backhaul link may be allocated an air interface channel from either the forward or reverse links of the air interface, depending on which of the forward and reverse links is more heavily loaded. Generally, one would allocate air interface channels for backhaul traffic transmission from the more lightly loaded of the forward and reverse links.  
           [0012]    In other exemplary embodiments, one of the parent and child RBSs includes a backhaul module configured with a high-gain receive or transmit antenna, and the other one of the RBSs transmits or receives, respectively, on its primary antenna. With such configurations only one backhaul module is needed at either the child or parent RBS. In still other configurations, only one backhaul module is used, but the module includes a high-gain antenna or antennas for duplex transmit and receive operations. In such configurations, the child RBS might, for example, use its associated backhaul module to transmit reverse backhaul traffic to the parent RBS and receive forward backhaul traffic from the parent RBS. In turn, the parent RBS could transmit and receive backhaul traffic using its primary antenna without need for an associated backhaul module or additional antennas.  
           [0013]    Generally, the child and parent RBSs include transceiver resources, such as modulators and demodulators, transmitters and receivers, and various supporting hardware and software for supporting the air interface operations. Where the child RBS includes a full-duplex backhaul module, the RBS generally includes one or more backhaul processors that process reverse and forward backhaul traffic to and from the parent RBS, and interface with transmit and receive data processors managing mobile station traffic transmitted and received on the air interface. Where the child RBS includes a simplex backhaul module and receives forward backhaul traffic on its primary antenna, it generally includes a receive data processor to separate mobile station and backhaul traffic and one or more backhaul processors to operate on the separated backhaul traffic received from the parent RBS and to format received mobile transmissions and overhead data as reverse backhaul traffic for transmission to the parent RBS via the backhaul module.  
           [0014]    In complementary fashion, the parent RBS includes, in one or more exemplary embodiments, one or both forward and reverse backhaul processors, as well as a backhaul interface to the conventional backhaul link communicatively coupling the parent RBS to the wireless network. Backhaul processing in the parent RBS includes formatting traffic received through the conventional backhaul link for transmission as forward backhaul traffic over the allocated air interface channel. Similarly, the parent RBS re-formats reverse backhaul traffic received over the air interface from child RBSs for transmission via the conventional backhaul link. In at least some embodiments, such re-formatting involves multiplexing a plurality of users&#39; data streams (voice and/or packet data) onto the allocated air interface channel(s) for forward backhaul transmission to the child RBS(s), and de-multiplexing complementary reverse backhaul traffic received from the child RBS(s). 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    [0015]FIG. 1 is a diagram of a conventional wireless communication network.  
         [0016]    [0016]FIG. 2 is a diagram of an exemplary wireless communication network for practicing the present invention.  
         [0017]    FIGS.  3 A- 3 D are diagrams of various exemplary embodiments for configuring child and parent radio base stations in the network of FIG. 2 for air interface based backhaul communication.  
         [0018]    [0018]FIG. 4 is a diagram of an exemplary child radio base station for use in the network of FIG. 2.  
         [0019]    [0019]FIG. 5 is a diagram of another exemplary embodiment for a child radio base station for use in the network of FIG. 2.  
         [0020]    [0020]FIG. 6 is a diagram of an exemplary embodiment for a parent radio base station for use in the network of FIG. 2. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]    [0021]FIG. 1 illustrates a conventional wireless communication network generally referred to by the numeral  10 . Network  10  comprises one or more Base Station Systems (BSSs)  12 , and a Core Network  14 , which communicatively couple mobile stations  16  to one or more other communication networks such as a Packet Data Network (PDN)  18 , e.g., the Internet, and the Public Switched Telephone Network (PSTN)  20 . Network  10 , as illustrated, supports both circuit-switched communication, e.g., voice and fax, and packet-switched communication, e.g., IP-based communication.  
         [0022]    BSS  12  provides the radio link to mobile stations  16 , and translates between the radio link data formats and protocols and the core network&#39;s data formats and protocols. In support of such functions, BSS  12  comprises one or more Base Station Controllers (BSCs)  30 , each supporting one or more Radio Base Stations (RBSs)  32 . The RBSs  32  are each coupled to the BSC  30  by a backhaul link  34 .  
         [0023]    In operation, the radio link, collectively denoted as air interface  36 , carries mobile station traffic between the RBSs  32  and the various mobile stations  16  supported by them. Air interface  36  represents not only the radio spectrum allocated to wireless communication between BSS  12  and the mobile station  16 , but also includes the controlling protocols, channel organizations, data formatting, etc., that define the details of radio communication used by network  10 . Those skilled in the art will appreciate that numerous standardized air interfaces exist, with notable examples of air interface standards including cdmaONE, cdma2000, Wideband CDMA (WCDMA), GSM, and TIA/EIA/IS-136.  
         [0024]    In general terms, a given RBS  32  receives traffic from one or more mobile stations  16  via a reverse link of air interface  36 , and reformats that received traffic for transmission to the BSC  30  via its dedicated backhaul link  34 . Similarly, traffic intended for mobile stations  16  supported by that given RBS  32  is forwarded from Core Network  14  to the BSC  30 , which transmits it to the given RBS  32  via the corresponding backhaul link  34 . The given RBS  32  formats this backhaul traffic for transmission over the forward link of the air interface  36  to the intended mobile stations  16 .  
         [0025]    Backhaul links  34  typically comprise dedicated lines, such as leased T1/E1 lines or dedicated microwave links that provide a reliable and relatively high bandwidth connection between an RBS  32  and its supporting BSC  30 . As such, backhaul links  34  represent a potentially significant component of network deployment costs, and, in some areas, represent significant construction challenges. For example, in regions of the world where the wired infrastructure is immature or non-existent, it may be impractical to install high-speed backhaul links  34  to a plurality of RBSs  32 . Thus, the opportunity to deploy wireless communication networks is limited in areas where the costs and technical difficulties associated with installing backhaul links  34  are prohibitive.  
         [0026]    The present invention addresses such concerns and limitations, and FIG. 2 is a diagram of an exemplary wireless communication network  40  in which the present invention may be practiced. As with the conventional network  10 , network  40  communicatively couples mobile stations  16  to various external networks  18  and  20  via the Core Network  14 . However, network  40  includes one or more BSSs  42  that include exemplary operating features and equipment significantly reducing the cost and complexity associated with deploying or expanding network  40 .  
         [0027]    BSS  42  includes one or more BSCs  44 , with each BSC  44  supporting one or more RBSs  46 . Here, RBSs  46  are designated as “parent” RBSs  46 A or “child” RBSs  46 B. Parent RBSs  46 A include a primary backhaul interface which links to BSC  44  through a backhaul link  48 , which may use T1/E1 or microwave links. In contrast, child RBSs  46 B have backhaul links to one or more other RBSs  46  via the mobile station air interface  50  ordinarily used for carrying traffic and control signaling to and from mobile stations  16 . In one or more exemplary embodiments of the present invention, air interface  50  comprises a cdma2000 air interface.  
         [0028]    In the context of the present invention, child RBSs  46 B use the mobile station air interface  50  for carrying backhaul traffic to and from other child RBSs  46 B and/or parent RBSs  46 A. In the context of this discussion, it should be understood that the term “backhaul traffic” includes the voice and data traffic associated with the various mobile stations  16 , and may further include overhead channel information (broadcast channel data), as well as radio base station control and maintenance information, which may be collectively referred to as “network signaling.” Thus, as used herein, backhaul traffic denotes a combined backhaul stream comprising a combination of mobile station traffic and network signaling that, in at least some embodiments, has been multiplexed together or otherwise consolidated for transport via one or more channels allocated from the air interface  50 .  
         [0029]    According to the illustration, RBS 1  and RBS 4  are configured as parent RBSs  46 A, and RBS 2 , RBS 3  and RBS 5  are configured as child RBSs  46 B. RBS 1  receives backhaul traffic from BSC 44  via the corresponding backhaul link for mobile stations  16  supported by it, and for those supported by RBS 2  and RBS 3 . Similarly, RBS 1  sends backhaul traffic to BSC  44  via the corresponding backhaul link based on mobile station traffic received at RBS 1 , RBS 2 , and RBS 3 . Likewise, RBS 4  sends and receives backhaul traffic to and from BSC  44  via its backhaul link  48  for mobile stations  16  supported by it and for those supported by RBS 5 .  
         [0030]    In an exemplary operation, RBS 1  receives primary backhaul traffic from BSC  44 . The primary backhaul traffic includes first data for mobile stations  16  supported by RBS 1  and second data for mobile stations  16  supported by RBS 2  or RBS 3 , as well as any required broadcast channel and RBS control/maintenance information. Thus, each RBS  46  receiving backhaul traffic via air interface  50  may process that traffic to extract any RBS control and signaling information it might contain that is intended for the receiving RBS  46 , and may also process the traffic to extract mobile station control and traffic data intended for the mobile stations supported by it. Here, RBS 1  extracts the first data and transmits it over a forward link of air interface  50  to the targeted mobile stations  16 .  
         [0031]    Further, RBS 1  processes the second data for transmission over air interface  50  as forward backhaul traffic for reception by RBS 2 . As noted, this second data may include traffic and control information intended for mobile stations  16  supported by RBS 2  and RBS 3 , and may include control and/or maintenance signaling for RBS 2  and RBS 3 .  
         [0032]    In turn, RBS 2  extracts data targeted to it and its supported mobile stations  16  from the forward backhaul traffic it receives from RBS 1 , and relays or otherwise passes along the remaining forward backhaul traffic intended for RBS 3  by transmitting it to RBS 3  via air interface  50 . Operations between RBS 4  and RBS 5  are consistent with such operation, although RBS 5  does not relay backhaul traffic to and from other child RBSs  46 B. Reverse backhaul traffic from RBS 3  to RBS 2  and on to RBS 1 , and from RBS 5  to RBS 4  is transmitted in similar fashion using air interface  50 .  
         [0033]    Notably, RBS 1  may transmit forward backhaul traffic to RBS 2  on either a forward link channel or a reverse link channel of air interface  50 . In either case, RBS 1  transmits forward backhaul traffic to RBS 2  on a given channel or channels allocated from air interface  50 , and RBS 2  receives that forward link backhaul traffic on the same channel or channels. Similarly, RBS 2  uses one or more allocated forward or reverse link air interface channels to transmit reverse backhaul traffic to RBS 2 . Likewise, backhaul traffic between RBS 2  and RBS 3  passes on additional channels allocated from air interface  50 . In this manner, backhaul traffic transmissions from any given RBS  46  to another RBS  46  via air interface  50  are received in essentially the same manner as mobile station traffic, although such backhaul traffic generally is processed differently from mobile station traffic.  
         [0034]    Moreover, the selection and use of forward and reverse link channels from air interface  50  for transmission of backhaul traffic may be based on the relative capacity utilization of the forward and reverse links of air interface  50 . For example, in cdma2000 networks, the forward link of the air interface typically is more fully utilized than the reverse link because of the data asymmetry associated with many types of packet data services such as web browsing, i.e., the mobile stations  16  typically receive more data than they send. Indeed, the RBSs  46  may transmit backhaul traffic according to the air interface but using one or more different carrier frequencies than used for the mobile station traffic.  
         [0035]    By using air interface  50  for backhaul communication, multiple child RBSs  46 B may be supported by a single parent RBS  46 A meaning that only one backhaul link  48  need be established between BSC  44  and the parent RBS  46 A. Thus, as was earlier noted, network  40  may be deployed or expanded with minimal expense and construction difficulty. Moreover, the air interface  50  represents a “resource” already owned or otherwise controlled by the network operator, such that using it for carrying backhaul traffic in addition to mobile station traffic actually increases utilization efficiency of air interface  50 . For example, where one or more RBSs  46  are deployed in relatively remote areas or other light usage areas, the volume of mobile station traffic often does not approach the full capacity of the air interface  50 , and using a portion of the reserve capacity of the air interface  50  for backhaul traffic thus increases its utilization efficiency.  
         [0036]    Thus, the deployment of child RBSs  46 B is preferably done in geographic areas where mobile station traffic is not expected to completely utilize the air interface&#39;s available data channels. Using one or more channels of the air interface  50  for carrying backhaul traffic does reduce the number of channels available for allocation to mobile stations  16 , but such a reduction imposes little practical downside in service areas where the total air interface capacity of the involved RBSs  46  is not being fully used.  
         [0037]    Further flexibility derives from the various arrangements of parent and child RBSs  46 , with only two of the several possibilities illustrated in FIG. 2. For example, FIG. 2 illustrates RBS 1 , RBS 2  and RBS 3  in a “daisy chain” configuration where RBS 2  relays forward backhaul traffic to RBS 3  from RBS 1  and reverse backhaul traffic to RBS 1  from RBS 3 . However, one or both RBS 2  and RBS 3  could support additional child RBSs  46 B, either directly as in a “star” configuration, or indirectly through additional daisy chains. Likewise, RBS 1  and RBS 4  could, as parent RBSs  46 A, support additional child RBSs  46 B directly or indirectly. It should be understood that the present invention encompasses all such arrangements.  
         [0038]    Generally, the number and arrangement of child RBSs  46 B that may be supported by a given parent RBS  46 A depend on the particulars of network  40 . More specifically, there may be a practical limit regarding the number of child RBSs  46 B that may be supported by given parent RBSs  46 A. Such limitations may simply involve the practical consideration of leaving sufficient capacity on the air interface  50  for supporting mobile station communication concurrent with backhaul communication.  
         [0039]    Additional limitations regarding the number of child RBSs  46 B that may be linked in daisy chain fashion to a parent RBS  46 A may arise due to timing limitations of the air interface  50 . For example, in cdma2000 standards, voice traffic is carried in successive 20 millisecond frames and each child RBS  46 B may impose up to one voice frame of delay in processing forward or reverse backhaul traffic. Thus, beyond a certain number of “hops” through child RBSs  46 B, the cumulative delay may become unacceptable.  
         [0040]    Regardless of the particular arrangements of parent and child RBSs  46 , use of the air interface  50  to carry backhaul traffic greatly simplifies network deployment. However, the specific manner in which the air interface  50  is used for backhaul traffic depends on its details. For example, if network  40  is based on cdma2000 standards, a parent RBS  46 A and its supported child RBSs  46 B each preferably allocate one or more high-speed data channels (Packet Data Channels) for carrying backhaul traffic from the air interface&#39;s defined set of communication channels. Channels not allocated to backhaul traffic usage remain available for supporting mobile station communication.  
         [0041]    In an exemplary embodiment, a given parent RBS  46 A allocates one or more available data channels from air interface  50 , and uses these allocated channels to send forward backhaul traffic to a given child RBS  46 B and receive reverse backhaul traffic from that child RBS  46 B. As highlighted earlier, forward backhaul traffic carried on air interface  50  from, for example, RBS 1  to RBS 2 , may be destined for distribution to mobile stations  16  supported by RBS 2 , or may be destined for mobile stations  16  supported by RBS 3 . In the latter case, RBS 2  typically allocates another of its available data channels from air interface  50  for relaying forward backhaul traffic onto RBS 3 . Further, note that the forward backhaul traffic received by RBS 2  typically includes a mix of communication traffic intended for mobile stations  16  supported by RBS 2  and mobile stations  16  supported by RBS 3 . In this scenario, RBS 2  processes the forward backhaul traffic to separate data intended for its mobile station  16  from the backhaul traffic intended for RBS 3 .  
         [0042]    [0042]FIG. 3A illustrates an exemplary configuration of a parent RBS  46 A and a child RBS  46 B. Parent RBS  46 A includes or is associated with a primary antenna  60  that serves as a “cell site” antenna providing radio reception and transmission via air interface  50 . Parent RBS  46 A further includes or is associated with a backhaul module  62  and its associated antenna  64 . Similarly, child RBS  46 B includes or is associated with a primary antenna  60 , and a backhaul module  62  and its associated antenna  64 . With this exemplary configuration, the parent RBS  46 A uses its backhaul module  62  to send forward backhaul traffic to RBS 2  via forward link  50  for reception by the child RBS  46 B on the child&#39;s primary antenna  60 . Likewise, the child RBS  46 B uses its backhaul module  62  to send reverse backhaul traffic on air interface  50  to the parent RBS  46 A for reception on the parent&#39;s primary antenna  60 .  
         [0043]    From the perspective of the child RBS  46 B, the parent&#39;s backhaul module  62  essentially functions as a mobile station  16  having only a simplex link for transmitting forward backhaul traffic over air interface  50  to the child. Generally, where the backhaul module  62  is used to transmit backhaul data, its antenna  64  comprises a high-gain, directional antenna that is well suited for transmitting a relatively high-gain signal that is easily received by the primary antenna  60  of another RBS  46 .  
         [0044]    Thus, in the illustrated embodiment, the child and parent RBSs  46  each have a backhaul module  62  with associated directional antenna  64  for transmitting backhaul traffic to each other. Note that parent RBS  46 A may transmit forward backhaul traffic to the child on a forward or reverse link channel of air interface  50 . Likewise, the child RBS  46 B may transmit reverse backhaul traffic to the parent on a forward or reverse link channel of air interface  50 . In one particularly advantageous embodiment, both the parent RBS  46 A and the child RBS  46 B may use reverse link channels from the air interface  50 .  
         [0045]    [0045]FIG. 3B illustrates another exemplary embodiment of parent RBS  46 A and child RBS  46 B. Here, parent RBS  46 A includes or is associated with a backhaul module  62  that provides duplex transmission and reception of forward and reverse backhaul traffic to and from child RBS  46 B via air interface  50 . With such a configuration, antenna  64  at the backhaul module  62  of the parent includes both transmit and receive capabilities (transceiver resources). Reverse backhaul traffic transmitted over air interface  50  from the child&#39;s primary antenna  60  is received at the backhaul module  62  of the parent via antenna  64 . As with other exemplary configurations of the present invention, the parent RBS  46 A and the child RBS  46 B retain the ability to support mobile station communication over air interface  50  concurrent with transmitting and receiving backhaul traffic.  
         [0046]    [0046]FIG. 3C illustrates yet another exemplary configuration of parent RBS  46 A and child RBS  46 B. Here, parent RBS  46 A transmits forward backhaul traffic to and receives reverse backhaul traffic from the child RBS  46 B using its primary antenna  60 . The child RBS  46 B transmits reverse backhaul traffic to the parent RBS  46 A using the child&#39;s backhaul module  62  and directional antenna  64 , and receives forward backhaul traffic through its backhaul module  62  via its directional antenna  64 .  
         [0047]    In this configuration, child RBS  46 B uses first transceiver resources in backhaul module  62  to transmit and receive backhaul traffic through directional antenna  64 . Such an arrangement differs from exemplary configurations where the backhaul module(s)  62  at the parent RBS  46 A supports full duplex transmission and reception of backhaul traffic. The configuration of backhaul modules  62  at the parent and child RBSs  46  may be configured as simplex or duplex, and such configuration options help balance the use of RBS resources in support of backhaul traffic transmission/reception.  
         [0048]    [0048]FIG. 3D is a diagram of an exemplary embodiment of a child RBS  46 B serving as a “relay” for backhaul traffic. It should be understood that the use of two backhaul modules  62  at the child RBS  46 B is not necessary for relay operations, but merely represents one advantageous arrangement for relaying backhaul traffic. Here, the child RBS  46 B uses one backhaul module  62  to receive reverse backhaul traffic from another child RBS  46 B, and another backhaul module  62  to transmit the relayed reverse backhaul traffic to an upstream child RBS  46 B or to a supporting parent RBS  46 A.  
         [0049]    The child RBS  46 B may further receive forward backhaul traffic for relaying to downstream child RBSs  46 B via its primary antenna  60 . Thus, the child relays forward backhaul traffic received on its primary antenna to a downstream child through one of its backhaul modules  62 , and relays reverse backhaul traffic received from the downstream child on one of its backhaul modules  62  using its other backhaul module  62 . As with the other configurations, the child RBS  46 B supports concurrent mobile station communication on air interface  50 .  
         [0050]    [0050]FIG. 4 is an exemplary embodiment of the processing and transceiver resources for an exemplary child RBS  46 B. In this embodiment, the child RBS  46 B includes first transceiver resources for sending and receiving backhaul traffic and second transceiver resources for sending and receiving mobile station traffic. Here, the child RBS  46 B includes a full-duplex backhaul module  62  that includes the first transceiver resources coupled to directional antenna  64 . The second transceiver resources are shown as transceiver resources  70  coupled to the primary antenna  60 . Child RBS  46 B further includes a transceiver processor comprising receive processor  72  and transmit processor  76 , and a backhaul processor  78 .  
         [0051]    As regards the overall depicted arrangement, it should be understood that the diagram depicts a functional organization that may not correspond to the actual physical implementation of equipment within the RBS  46 . Further, it should be understood that the various processors illustrated, e.g., transmit processor  76 , etc., are illustrated as single functional blocks but may actually be implemented as a collection of physical processors, processing systems or sub-systems, etc., that cooperate to perform the represented functionality. Such arrangements of processing elements and supporting software within wireless communication network entities is well understood by those skilled in the art.  
         [0052]    In any case, with the full-duplex capability of backhaul module  62 , child RBS  46 B receives forward backhaul traffic and transmits reverse backhaul traffic through backhaul module  62  using the directional secondary antenna  64 . Thus, the backhaul processor  78  is coupled to the transceiver resources included in the backhaul module  62 , and processes the backhaul traffic transmitted and received through the module. Forward backhaul traffic received by child RBS  46 B is processed by backhaul processor  78  for input to transmit processor  76  which is configured to format the traffic for transmission as mobile station traffic via transceiver resources  70  and primary antenna  60 . Similarly, mobile station traffic received on primary antenna  60  is processed by transceiver resources  70  for input to receive processor  72 , which provides the received mobile station traffic to backhaul processor  78 . The backhaul processor  78  formats the mobile station traffic for transmission by backhaul module  62  as reverse backhaul traffic via air interface  50 .  
         [0053]    [0053]FIG. 5 is another exemplary embodiment of a child RBS  46 B, which transmits reverse backhaul traffic via its included backhaul module  62  and associated secondary antenna  64 , and receives forward (and/or relayed) backhaul traffic via its primary antenna  60 . Thus, the first transceiver resources used to send and receive backhaul traffic are implemented partially in backhaul module  62  (for backhaul transmission) and partially in the transceiver resources  70  (for backhaul reception) that are also used for mobile station traffic.  
         [0054]    Together the reverse backhaul processor  80  and forward backhaul processor  82  comprise the earlier discussed backhaul processor  78 . In operation, then, the child RBS  46 B uses a simplex backhaul transmission link supported by transmitter resources included in backhaul module  62  and receiver resources in transceiver resources  70 . In this arrangement, receive processor  72  passes at least a portion of received forward backhaul traffic to the forward backhaul processor  82  for demultiplexing and subsequent transmission as broadcast and/or mobile station traffic via primary antenna  60 .  
         [0055]    Relayed backhaul traffic and incoming data from mobile stations  16  received on primary antenna  60  passes from the receive processor  72  to the reverse backhaul processor  80 , which processes that data, along with any local RBS control and operating information, as reverse backhaul traffic for transmission from directional antenna  64  via module  62 . Note that the child RBS  46 B could reverse the illustrated arrangement such that it receives forward backhaul traffic via backhaul module  62  and transmits reverse (or relayed) backhaul traffic via its primary antenna  60 . In such a scenario, the simplex implementation of backhaul module  62  would include receiver resources rather than transmitter resources.  
         [0056]    [0056]FIG. 6 discloses an exemplary embodiment of a parent RBS  46 A. Parent RBS  46 A includes primary antenna  60 , backhaul module  62 , transceiver resources  70 , receive processor  72 , transmit processor  76 , and reverse and forward processors  80  and  82  similar to one or more embodiments of the child RBSs  46 B. Additionally, parent RBS  46 A includes a primary backhaul interface  90  adapted to interface parent RBS  46 A to the supporting BSC  44  through one of the dedicated backhaul links  48 . In many respects, operation of the various elements of parent RBS  46 A are consistent with the earlier descriptions for the same elements in the context of the child RBSs  46 B. However, here the reverse and forward backhaul processors  80  and  82  may perform additional formatting or translation functions associated with adapting the backhaul traffic sent to and from the child RBSs  46 B to the standardized primary backhaul interface  90 .  
         [0057]    For example, primary backhaul traffic received from the BSC  44  may be targeted to one or more child RBSs  46 B supported by the parent RBS  46 A, and the parent may multiplex such backhaul traffic into one or more data streams suitable for transmission over air interface  50 . In an exemplary embodiment, data streams corresponding to different voice and/or data calls are multiplexed into a combined backhaul traffic stream suitable for transport over one or more data channels allocated from the air interface  50 .  
         [0058]    In a cdma2000 implementation, multiple 9.6 kbps (or other standardized data rate) voice calls may be multiplexed onto a single 144 kbps supplemental packet data channel (SCH) available for use in air interface  50 . Thus, the parent RBS  46 A receives backhaul traffic including voice traffic for multiple mobile stations, selects the backhaul traffic targeted to its child RBSs  46 B, and processes that traffic for transmission as forward backhaul traffic over the air interface  50  by multiplexing it onto one or more supplemental channels. In turn, the receiving child RBS  46 B (or RBSs) processes the received forward backhaul traffic by extracting data targeted to it (i.e., mobile station traffic and network signaling data), and relays the rest of it to downstream child RBSs  46 B, if any, on one or more other allocated air interface channels.  
         [0059]    In complementary operations, the reverse backhaul processor  80  of parent RBS  46 A processes the reverse backhaul traffic received from the one or more child RBSs  46 B supported by the parent. In an exemplary embodiment, such processing involves demultiplexing the combined data stream(s) that comprises the reverse backhaul traffic received from the child RBSs  46 B. After demultiplexing the combined stream into the data streams corresponding to the different mobile stations  16 , the backhaul processor  80  formats it for transmission as primary backhaul traffic over link  48  to BSC  44 .  
         [0060]    In general, the present invention applies multiplexing and demultiplexing, which may be referred to as “trunking” and “de-trunking,” to significant advantage. That is, a single logical channel of the air interface  50  may be used to carry backhaul traffic representing a collection of RBS control, signaling, and broadcast channel data for one or more RBSs  46 , as well as mobile station traffic for multiple mobile stations  16  supported by those one or more RBSs  46 .  
         [0061]    Thus, as an example of exemplary trunking/de-trunking operations, RBS 1  trunks or “bundles” RBS control streams, broadcast channel streams and mobile station traffic streams for RBS 2  and RBS 3 , onto one or more logical channels of air interface  50  for transmission as forward backhaul traffic to RBS 2 . RBS 2  receives such backhaul traffic, de-trunks it to recover control and traffic streams intended for it or for mobile stations  16  supported by it, and re-trunks the balance of such traffic for relay transmission to RBS 3  via another channel of air interface  50 . Similar trunking/de-trunking operations play out for the reverse backhaul traffic arriving at RBS 1  via the RBS 3 /RBS 2  relay chain.  
         [0062]    Note that where the parent and child RBSs  46  carry voice-based backhaul traffic over packet data channels of air interface  50 , transmission of that backhaul traffic may be altered slightly from that used for conventional mobile station packet data traffic to maintain acceptable voice quality. For example, packet data retry may be disabled on the air interface channels carrying voice-based backhaul traffic. Packet data retry, generally implemented at the Radio Link Protocol (RLP) layer of BSS  42 , is appropriate for true packet data transfers where such a retry mechanism ensures data integrity but is inappropriate for the ordered delivery of time-sensitive voice data. Thus, the data retry feature of RLP may disabled in an exemplary cdma2000 implementation where supplemental packet data channels (SCH) are used to carry backhaul traffic.  
         [0063]    With data retry disabled, the RBSs  46  may set a more stringent received signal quality for the backhaul traffic signals to ensure that acceptable error levels are maintained. Tightening the signal quality requirements may be accomplished in a variety of ways. For example, the RBSs  46  (or supporting BSC  44 ) may set the maximum acceptable Frame Error Rate (FER) for backhaul channels at one percent or less rather than the more conventional two percent FER setting associated with mobile station voice traffic.  
         [0064]    However, those skilled in the art should appreciate that such “tuning” may or may not be applied to the air interface channels used for backhaul traffic, depending on performance goals and the type of traffic (packetized voice or actual packetized data) carried as backhaul traffic on the air interface  50 . Of course, where network  40  uses air interface  50  to carry voice and data backhaul traffic, it may segregate the two types of traffic and allocate specific air interface channels for carrying voice-related backhaul traffic and other air interface channels for carrying data-related backhaul traffic. As such, it might apply the above described tuning to only some of the backhaul channels.  
         [0065]    In general, those skilled in the art will recognize that the above discussion highlights exemplary operations and configurations of network  40  in the context of the present invention. However, the present invention is not limited by such details. Indeed, the present invention broadly defines the use of a wireless network&#39;s mobile station interface to carry backhaul traffic, including control and signaling information. With this approach, RBSs transmit and receive backhaul traffic using one or more channels allocated from the available air interface channels, and transmit and receive mobile station traffic using the same air interface.