Abstract:
A radio access network includes a transport network layer; a radio network layer having a layer 2 network for communicating between entities within the radio network layer by exchanging datagrams having a predetermined format used only within the radio network layer. Accordingly, the present invention provides for a true decoupling at layer 2 between the radio network layer and the transport network layer. 
     Addressing at layer 2 can enable both connectionless and connection oriented using an overlay connectivity model. Layer 2 in the radio network layer is implemented as an Ethernet network.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of application Ser. No. 10/321,481, filed on Dec. 18, 2002, which claims the benefits of earlier filed provisional application No. 60/356,702, filed Feb. 13, 2002, the entire contents of which are hereby incorporated by reference for all purposes. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to transport for wireless radio access networks. 
     BACKGROUND OF THE INVENTION 
       FIG. 1  illustrates a known reference model for a radio access network (RAN). A base station controller/radio network controller (BSC/RNC)  10  is coupled to a plurality of wireless base station  12 ,  14 ,  16 ,  18  via a radio access network  20 . The radio access network can be modeled as a radio network layer (RNL)  22  and a transport network layer  24  and three planes intersecting those layers, a radio network control plane  26 , a transport network control plane  28  and a user plane  30 . The network may be leased from a service provider (SP) or owned by the wireless service operator. 
     In operation, the transport network layer (TNL) receives a request from the RNL to establish a bi-directional transport bearer for datagram traffic. The request includes the end system address and transport bearer association received from the peer. It also includes the quality of service and resources required from the transport network. In summary it shall:
         Provide unique connection identifiers such that individual flows can be uniquely addressed for both user plane as well as control plane (eg VPI, VCI, CID in AAL2/ATM);   Provide in-sequence delivery of PDUs to upper layers;   Support sending coordinated dedicated channels (DCHs) multiplexed onto the same transport bearer (i.e., frame multiplexing, e.g. AAL2/ATM);   Provide proper mappings of required RNL bearer channels QoS to TNL resources (eg AALx in ATM); Provide transport signalling protocol used to setup and tear down transport bearers (eg ALCAP in 3GPP r3);   Provide segmentation and re-assembly mechanism in order to fit to the maximum PDU size (i.e., R3 ATM AAL2 SSSAR layer function);       

       FIG. 2  illustrates a known RAN network system model. The RAN network system model includes the wireless base station controller  10 , the wireless base station  12  and an intervening transport network (TRAN)  40 . The TRAN  40  includes points of attachment (PoA)  42  and  44  and intranetwork switching collectively represented by function block  46 . For the system model of  FIG. 2  the current network connectivity model is a peering model. For the peering model: User traffic is “peered” with Service Provider&#39;s network at point of attachment (PoA) via rudimentary/sophisticated User Network Interface (UNI). In this model, user quality of service (QoS) requirements are snooped by the SP or signaled from user to the SP (via the UNI interface) in order to satisfy required QoS guarantees. 
     Consequently wireless datagrams need to be processed by both wireless end points and SP TRAN equipment. This means all sub-systems need to have common understanding of: QoS information, Signaling capabilities and Flow segregation ID across PoA. The known RNL peering connectivity model imposes upon the TNL the need to also implement a peering connection-oriented model; current implementations of datagram addressing are peering-like, coupling RNL  22  (DCH-ID, etc) and TNL  24  (AAL2 CID, etc) identifiers. 
     Emerging connectionless protocols, such as IP are being proposed as the new TNL transport mechanism and will have to meet connection-oriented requirements 
     In order to use connectionless IP, development of mechanisms to offer connection-oriented capabilities to wireless TNL layer needs to take place. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an improved transport for wireless radio access networks. 
     In accordance with an aspect of the present invention there is provided a method of operating a radio access network comprising: establishing a radio network layer; establishing a transport network layer; and communicating between entities within the radio network layer by exchanging datagrams having a predetermined format used only within the radio network layer. 
     In accordance with an aspect of the present invention there is provided a radio access network comprising: a transport network layer; a radio network layer including a layer 2 network for communicating between entities within the radio network layer by exchanging datagrams having a predetermined format used only within the radio network layer. 
     Accordingly, the present invention provides for a true decoupling at layer 2 between the radio network layer and the transport network layer. 
     In accordance with an aspect of the present invention a method of processing layer 2 datagrams within RNL is provided that facilitate decoupling thereof. 
     Addressing at layer 2 can enable both connectionless and connection oriented using an overlay connectivity model 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be further understood from the following detailed description with reference to the drawings in which: 
         FIG. 1  illustrates in a block diagram a known reference model for a radio access network (RAN); 
         FIG. 2  illustrates in a block diagram a known RAN system model; 
         FIG. 3  illustrates in a functional block diagram a wireless base station and a base station controller communicating via a datagram service in accordance with an embodiment of the present invention; 
         FIGS. 4   a  and  4   b  illustrates in block diagrams transport options for the datagram service of  FIG. 3 ; 
         FIG. 5  illustrates in a block diagram the main functional components of the wireless base station and the base station controller of  FIG. 3 ; 
         FIG. 6  illustrates the functional components of the host platform switch of  FIG. 5  in further detail; 
         FIG. 7  illustrates Ethernet encapsulation for the datagram service for length encapsulation; 
         FIG. 8  illustrates Ethernet encapsulation for the datagram service for type encapsulation; 
         FIG. 9  illustrates in a functional block diagram second tier address assignment in accordance with an embodiment of the present invention; 
         FIG. 10  illustrates in a block diagram various point of attachment operational configurations possible using the datagram service of  FIG. 3 ; and 
         FIG. 11  illustrates in a block diagram how a soft hand-off is handled using the datagram service of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIG. 2 , there is illustrated in a block diagram a known RAN system model implemented in an overlay model in accordance with an embodiment of the present invention. 
     For the overlay model: User datagram requirements are much simplified. The service provider (SP) offers quality of service (QoS) guarantees as part of the service in a point-to-point or point-to-multipoint (via Dedicated or Virtual Private Line service framework). Hence, the user datagram does not need to carry any flow segregation ID peering with SP, nor does it need to offer any signaling capability, nor any QoS information as the service leased corresponds to common denominator user flows characteristics, i.e. highest QoS. 
     Consequently, datagrams processed by wireless can be totally independent from SP TRAN datagram processing functions enabled via PoA edge translation (physical port-based mapping): This means each point of attachment (PoA)  42  and  44  provides an operational independence of: QoS, signaling and flow segregation technologies. 
     The wireless base station controller  10  and wireless base station  12  include wireless radio frames computing platforms. Host systems intercommunicate using either L2 frames or L3 packets as datagrams. 
     The network points of attachment (POA)  42  and  44  either map wireless datagrams into lower layer transport services (examples: DSx, STSx, OCs for dedicated PL) or actively switches the datagrams (examples: Ethernet Switching, MPLS, IP routing for virtual PL). 
     The transport provided by the TRAN  40 , as represented by a pipe  48  provides physical port-based, point-to-point flow of datagrams over dedicated or virtual Ethernet private line sessions with a specific service level agreement (SLA). 
     Intra-switches as represented by the block  46  provides backhaul networking intra-switching (examples are: TDM switched, SONET/SDH Ring or Meshed networks). 
     The cellular terrestrial radio access network (TRAN)  40 , typically uses private addressing space (examples, A/Z PL, IPV4/6, Ethernet Mac). 
     Referring to  FIG. 3 , there is illustrated in a functional block diagram a wireless base station and a base station controller communicating via a datagram service in accordance with an embodiment of the present invention. The base station function block  12 ′ includes a radio frequency domain  50 , a digital domain  52  and a datagram service  54 . The base station controller function block  10 ′ includes a mobility function  60 , a packet processing function  62 , a wireless application core steering  64  and a datagram service  66 . A datagram is an independent, self-contained message sent over the network whose arrival, arrival time, and content integrity guarantees are assured by network service and not by the datagram protocol capabilities. Datagrams can be either wireless radio frames or OA&amp;M signals. 
     Referring to  FIGS. 4   a  and  4   b , there are illustrated in block diagrams transport options for the datagram service of  FIG. 3 . Behind the POA-edge ( 42  and  44 ), once the traffic is encapsulated, the carrier is free to use the most economic L1, L2, L3 switching fabric that provides desired SLA. The embodiments of the present invention are based on an overlay network system design, enabling carrier providers to operate TRAN ( 40 ) networks independent of wireless operator&#39;s equipment ( 10  &amp;  12 ).  FIG. 4   a  illustrates how a carrier frame  80  having an embedded Ethernet frame  82  can be transported using SONET  84  as payload  86  or optical channels  88  as payload  90 .  FIG. 4   b  illustrates how carrier frame  94  and Ethernet frame  96  are combined to form a frame  97 , where the optical Ethernet label  98  includes an Ethernet MAC adding  100  and where the optical Ethernet MPLS label  102  includes the Ethernet MAC address  104 . 
     Referring to  FIG. 5 , there is illustrated in a block diagram the main hardware components of the wireless base station and the base station controller of  FIG. 3 . 
     The base station  12  includes a host platform switch  110 , a plurality of process modules  111  each having a plurality of application processes (AP)  112 . Similarly the base station controller  10  includes a host platform switch  120 , a plurality of process modules  121  each having a plurality of application processes (AP)  122 . 
     The application processes include radio modems, RLC &amp; RRL S/W. Radio PDU may or may not contain AP-ID information for necessary for flow steering function performed at PM level  111  and  121  (second tier address options) 
     Each process module  112 ,  122  has a single Ethernet MAC address (OUI=0). A simple packet steering function is performed by the PM  112 ,  122  in order to send PDU to individual AP  112 ,  122  (2 second tier address options) 
     Host platform switches  110  and  120  are Ethernet switching points that do not possess Ethernet MAC addresses (except for OAM&amp;P agent, etc) as it performs layer-2 bridging algorithm. A direct 1:1 PM address and Host Switch port mapping is used for design simplicity. 
     For dedicated Ethernet private line the inter-host frame walk through is as follows: AP  112 ,  122  are identified by STA (second tier address). PM  111 ,  121  have a single Ethernet MAC address. PM frame steering function is based on STA information. There is simple 1:1 relationship between Host Switch  110 ,  120  port and PM  112 ,  122  MAC address. Host switches frames based on FTA address information (i.e. Ethernet DA and SA) where a forwarding decision is based on destination address (DA) MAC/egress Port and learning tables that are populated via source addresses (SA) MAC/ingress Port information; 
     Host Switch  110  forwards frames to PoA  44  using PM DA MAC address information. TNL  40  simply encapsulates user flow with no regard of user address/QoS information as service is offered on dedicated port basis (non shared). Private Ethernet addressing space enables wireless operator to assign any type of networking identifier (examples: URL, IP, MPLS/LSP, ATM VP/VC, L2 Macs). 
     The overlay TNL network  40  point of attachment  40 ,  44  forwarding is based on dedicated physical or virtual port mapping (examples DSx, STSx, LSP). 
     AP  112 ,  122  addresses are mapped to Ethernet FTA &amp; STA address space. Ethernet FTA can be learned or manually provisioned at AP driver interface. If automatically provisioned, Ethernet DA MAC addresses can utilize standard registration protocol (ie GARP, GVRP, or even other simpler methods). 
     The simple method referred here aims at leveraging the simple 802.1D bridging algorithm where MAC addresses are learned and aged out as a fundamental behaviour that can be exploited for end-host Ethernet MAC address discovery and thus simplify tremendously the software investment on each nodal system to perform such a task at boot time. The highlights are as follows:
     1) end host (e.g. BTS) that needs to discover the other end host(s) (e.g. BSC/RNC) can simply issue from the AP a specially VLAN-tagged broadcast packet to network (e.g. backhaul).   2) This special VLAN-tagged broadcast (or VLAN-contained broadcast) restricts ENET pollution to only VLAN-aware switches and registered end-host MAC station. It also requires all ENET switch along the path to be VLAN-capable.   3) Once the other host receives that special VLAN-tagged broadcast frame, it responds by issuing a Unicast back to the sender.   4) Once sender receives the unicast frame, the process is over as both end hosts now has both respective destination MAC address for remaining of datagram exchange.
 
Inter-Host Frame Walkthrough Over EPL Service Framework:
 
AP &lt;-&gt; PM
   

     APs are identified by STA  148  (second tier address). PM have single Ethernet MAC address. PM datagram steering function performed by host switch is based on FTA information  146 . 
     PM &lt;-&gt; Host 
     There is simple 1:1 relationship between Host Switch port and PM MAC address. Host switches frames based on FTA address information where forwarding decision is based on DA MAC/egress Port and learning tables are populated via SA MAC/ingress Port information; 
     Host &lt;-&gt; PoA 
     Host Switch  110  forwards frames to PoA  44  using PM  110  DA MAC address information  146 . TNL  40  simply encapsulates user flow with no regard of user address/QoS information as service is offered on dedicated port basis (non shared). Private Ethernet addressing space enables wireless operator to assign any type of networking identifier (examples: URL, IP, MPLS/LSP, VLAN tags, L2 Macs). 
     TNL Overlay 
     TNL  40  Network point of attachment forwarding based on dedicated physical or virtual port mapping (examples Label insertion, MPLS-like, Martini, etc). QoS traffic management is implemented based on queuing model where statistical multiplexing is possible. 
     End Points Address Determination 
     AP addresses are mapped to Ethernet FTA &amp; STA address space (see  FIGS. 7 &amp; 8 ). Ethernet FTA can be learned or manually provisioned at AP driver interface. If automatically provisioned, Ethernet DA MAC addresses can utilize standard registration protocol (i.e. GARP, GVRP, or even other simpler methods) as described herein above. 
     Referring to  FIG. 6  shows functional components of the host platform switch of  FIG. 5  in further detail. The host platform switch has an Ethernet address, a bearer function  130  which performs the 802.1D forwarding algorithm, and a control function  132  which requires an Ethernet &amp; IP addresses to terminate host management house keeping tasks. Binding of Host Ethernet address with higher host-level provisioned address, such as IP address or URLs, can be accomplished by ARP or DHCP-like procedures. 
     Referring to  FIG. 7 , there is illustrated ethernet encapsulation for the datagram service for length encapsulation. Wireless datagrams for Mobile customer traffic (examples: direct radio frames (RFP) or RFP/AAL2/ATM or RFP/BCN, etc), as well as wireless host IP OA&amp;M &amp; control datagrams are encapsulated as Ethernet payloads  144 . 
     One or many wireless datagrams can be encapsulated (coordinated DCHs over single transport bearer*) 
     For 802.3 Ethernet Length Encapsulation the first tier address  146  includes 12 Bytes (2×48-bit) Destination &amp; Source MAC are used as first tier address (FTA)  146 , and a second tier address  148  (STA) that is 8 Bytes total that contains a fixed LLC Header  150  [(3B) (DSAP=0xAA, SSAP=0xAA, Ctrl=0x03)] &amp; SNAP Header  152  (5B) available for second tier address. The SNAP header  152  contains SNAP OUT (3B) and SNAP Pid (2B). 
     Intra-Host Ethernet Length STA Walk Through: 
     Host &lt;-&gt; PM 
     There is 1:1 relationship between Host Switch port and PM MAC address. Host switches frames based on FTA address information  146  where forwarding decision is based on DA MAC/egress Port and learning tables are populated via SA MAC/ingress Port information. 
     PM &lt;-&gt; Host 
     APs are identified by STA ( 148  second tier address). PM have single Ethernet MAC address. PM frame steering function is based on STA SNAP Header address  152  information, (i.e. fixed LLC header  150  fixed to DSAP=0xAA, SSAP=0xAA, Ctrl=0x03+SNAP header (5B- 152 ). When using the Length encapsulation, the 2 bytes  154  following the SA field represent the actual length of data payload. The LLC being fixed, the SNAP OUI &amp; SNAP Pid can be used (Pid=2 16  available address space) to address higher-layer protocol (e.g. application). 
     Referring to  FIG. 8 , there is illustrated Ethernet encapsulation for the datagram service for type encapsulation. 
     802.3 Ethernet Type Encapsulation: 
     12 Bytes Destination &amp; Source MAC are used as first tier address (FTA) 
     4 Bytes VLAN tags (VPID &amp; TCI) are available for second tier address (STA) 
     Intra-Host Ethernet Type STA Walkthrough 
     Host &lt;-&gt; PM 
     There is 1:1 relationship between Host Switch port and PM MAC address. Host switches frames based on FTA address information  146  where forwarding decision is based on DA MAC/egress Port and learning tables are populated via SA MAC/ingress Port information; 
     PM &lt;-&gt; Host 
     APs are identified by STA (160 second tier address). PM have single Ethernet MAC address. PM frame steering function is based on STA 802.1Q VLAN tag information  160 . When using the Type encapsulation, the 2 bytes  162  following the SA field identifies the nature of the client protocol running above Ethernet (e.g. IP uses Type field=0x0800). AP identification and steering is done via Tag Control Information (TCI)  164  field which contains 3-bits for QoS priority, 1 bit for control and remaining 12 bits for VLAN-ID, thus 2 12 =4096 available addressable space to address higher-layer protocol (e.g. applications). 
     Referring to  FIG. 9 , there is illustrated in a functional block diagram second tier address assignment in accordance with an embodiment of the present invention 
     A mobile terminal user entity  200  having an application layer  202  and an L2  204  becomes associated with a base station  12  having a radio network layer  22  RNL MAC layer  206 . The RNL MAC layer  206  needs to be bound to the Ethernet  208 , which makes use of a L1 wrapper  210 . 
     For second tier address (STA) assignment there are three possible methods. Endpoints for end-to-end datagram communication are uniquely identified by FTA and STA. STA can be assigned by a manual  212 , learning  214  or connection oriented  216  procedures. RNL link setup signaling can be used to manage Host &amp; Port address, that is, from an architectural perspective one does not have to rely on the existence of UDP/IP stack 
     Referring to  FIG. 10 , there is illustrated in a block diagram various point of attachment operational configurations possible using the datagram service of  FIG. 3 . 
     POA Operational Configurations—Dedicated-PtPt &amp; Groomed-PtMP 
     
         
           224  One POA  44  is connected to only one BTS  12 , with one port appearance on the BTS  12  HPS  110 . This is applicable to both configurations  220  and  230 . 
           220  One POA  42  port appearance on BSC  10  HPS  20  for each BTS  12 . 
           236  One POA  44  connected to more than one BTS  12 , with one port appearance on each BTS HPS  10 . This is applicable to both configurations  220  and  230 . 
           230  One POA  42  is connected to only one BSC  10 , with one port appearance on BSC HPS  20  for more than one BTS  12 .
 
POA Interface Addressing &amp; Management
 
       
    
     For  22 ,  236  all TRAN traffic passing through the POA  228 ,  238  is steered to the customer facing port (BTS  12  or BSC  10 ). All Ethernet first tiered addresses  146  receive the same steering treatment to the customer port. Second tiered addresses are not processed by the POA. The steering function is manually provisioned at startup and does not change. 
     For  220 , all TRAN traffic passing through the POA  222  is steered to the corresponding BTS based on Ethernet first tiered addresses  146 . Second tiered addresses are not processed by the POA. 
     Steering function is manually provisioned or realized through an Ethernet learned/auto discovery process, as described with regard to  FIG. 2 . 
     Optional UNI signaled be applied for all BTS groomed traffic (logical channels) flowing over the high speed medium using second tiered addresses. 
     Embodiments of the present invention embrace an overlay model that enables TRAN POA-to-POA addressing to be independent from wireless equipment addressing. Addressing within the TRAN can be accomplished two different ways:
         A dedicated Ethernet Private line tunnel where the TRAN network  40  is used to tunnel traffic between two POAs  42  and  44 .   A Virtual Ethernet switched service where the TRAN network  40  operates like a distributed Ethernet switch between POAs  42  and  44 .       

     In both cases the TRAN wireless traffic is encapsulated using any Layer 1, Layer 2, or Layer 3 networking scheme. Embodiments of the present invention described herein have emphasized an all Ethernet layer 2 approach, however the architecture foundation of the all Ethernet approach does not exclude encapsulating Ethernet frames at POAs  42  and  44  using either IP or SONET techniques. TRAN addressing scheme between POA can be any techniques; using one or both FTA and STAs methods. The only requirement is that TRAN FTA and STAs remain independent of encapsulated wireless equipment FTA and STAs. 
     Referring to  FIG. 11 , there is illustrated in a block diagram how a soft hand-off is handled using the datagram service of  FIG. 3 . For simplicity the TRAN  40  is represented by an Ethernet switch  46 . The process for a downlink TNL multicast (Soft Hand-Off) is illustrated. 
     Today&#39;s RNL (RLC, etc) needs to perform packet duplication while in soft hand off mode. 
     An Ethernet-switched TNL offers integrated multicast capabilities where only objects needs to be exchanged between the BSC  10  and BTS  10  and BTS  12  (DCH source , BTS-ID 1 , BTS-ID n , Event-ID). 
     If the Type STA option of  FIG. 7  is used two methods is possible: 
     GARP signaling events triggered at power measurement messages passing a threshold value invoking soft-hand off operation of drift-BTS  14 . This results in GARP registration exchange for all BTS participating in soft-hand off operation. GARP tear-down triggered by power measurement going below a threshold forcing to leave multicast. This method needs the creation of new GARP multicast address specific for wireless multicast soft hand-off application. 
     Use VLAN registration during soft hand off scenario where contained frame broadcast is performed inside VLAN paths only (VLAN-contained broadcast). Here GVRP is used as part of registration/removal exchange. 
     GLOSSARY 
     
         
         AP=wireless application process. That&#39;s usually physically instantiated at silicon/silicon island level but abstraction boundary can be extended up to board packaging level. 
         PM=Process Module. Includes many AP processes. Typically physically instantiated at the board level but abstraction boundary can be extended up to shelves and frame packaging level. 
         Host=Platform addressable entity. Include several PMs. Typically physically instantiated at the shelf level but abstraction boundary can be extended up to set of shelves and/or frame packaging level. 
         Frame=layer 2 protocol information definition (eg ATM, Ethernet, FR, PPP, etc). Data link addressing visibility and link error detection done on a per hop/segment basis; 
         Packet=Layer 3 protocol information definition (eg IP, IPX, etc). Network layer where addressing visibility is beyond hop/segment subnet. 
         STA=Second Tier Address component 
         FTA=First Tier Address component 
         RFP=Radio Frame Protocol 
         ALCAP=Generic name for the transport signalling protocols used to set-up and tear-down transport bearers 
         EPL=Ethernet Private Line service; 
         D-EPL=Dedicated Ethernet Private Line service. Not statistical multiplexing occurs and usually maps onto dedicated circuits (eg DSx/STx, etc); 
         V-EPL=Virtual Ethernet Private Line service. Statistical multiplexing benefits exists applying QoS traffic management principles over queuing model; 
         HPS=Host Platform Switch.