Solutions and Recommendations | WIRELESS ROUTER ARCHITECTURE

In the proposed architecture, the wireless routers (WRs) situated in different cells perform message routing in addition to the traditional Base Station (BS) functions. In fact, the traditional functions of the base stations, BSC (Base Station Controller), and MSC (Mobile Switching Center) in the legacy systems are lumped together and distributed across various WRs in the new wireless architecture. Figure 1 is a very high level depiction of various inter-router links as well as the control links between the proposed WRs, and the traffic and control interfaces. The inter-router links include: i) wireless specific virtual tunnels i. e. Multi Protocol Label Switch (MPLS) paths based on IP packets, ii) RSVP (Resources Reservation Protocol)/LDP (label Distribution Protocol) signaling channel, iii) routing message channel, iv) wireless specific virtual channel to carry MPLS based radio frames, and v) one or more wireless-specific control channels for call setup and maintenance including a signaling channel for usage by any signaling protocol (SP) such as extended RSVP and a routing channel for usage by any radio routing protocol (RRP) such as extended OSPF (Open Shortest Path First), RIP (Routing Information Protocol), or BGP (Boarder Gateway Protocol). The bold and dashed lines in the figure indicate the data and control channels, respectively.

Figure 1: Proposed wireless router links to peer routers and various control interfaces

 

For supporting wireless traffic services, the WRs access traffic and control interfaces that include media gateway controllers, WAP (Wireless Application Protocol) servers, policy management servers, call agent controllers, mobility managers, and AAA (Authentication, Authorization, and Accounting) servers. WRs communicate with these interfaces through MGCP (Media Gateway Controller Protocol), COPS (Common Open Policy Service), and other suitable protocols.

The WR architecture proposed herein facilitates wireless-access technology (e.g. CDMA or TDMA) independent network routing with the help of wireless interfaces to disparate wireless peripherals as shown in Figure 2, and hence is pivotal to an all-IP (Internet Protocol) radio access network (RAN) that seamlessly inter-works with the backhaul IP network with interfaces to various network peripherals. For communication with the backhaul networks at the other end, the WR includes wire-line interfaces to various network peripherals as well. At the heart of the WR lies the traffic control with various modules as follows: i) Quality of Service (QOS) engine for traffic conditioning and effective management of transmission resources, ii) Selection and Distribution Unit (SDU), iii) Central Processing Unit (CPU), iv) Call Processor, v) Timing Unit for synchronization purpose, vi) Communication Module with various traffic-controller interfaces to gateways, services, policy managers, IP routers, base-stations, call agents, and other remote nodes and resources, vii) Power and Interference Manager, viii) Radio resources Manager, ix) Mobility Manger, X) Packet Classification Unit, and xi) Security (IP SEC) Module.

Figure 2: Internal structure of the proposed wireless router

 

In the traditional mobile networks, an SDU is placed centrally at the Base Station Controller (BSC) to manage the call processing at a number of base stations. It selects the best frame from a number of incoming radio frame instances from the mobile via different base-stations (BSs) for onward transmission to the intended destination through backhaul network, and distributes similarly the messages received from the backhaul to the target mobiles. Based on the quality of the frames received from different base-stations, an SDU also manages soft-handovers (that is, call redirections from one BS to the other). In our architecture, BS is replaced by the more versatile WR module. Additionally, it incorporates an innovative concept of a distributed SDU with every WR housing an SDU. These distributed SDUs in the present architecture facilitate distribution of intelligence, and switching and control functionality to individual cell sites.

The main advantage here is that the radio frames need not be transmitted to the BSC over the backhaul links. A very efficacious use of the backhaul network bandwidth this way, in turn, results tremendous cost savings for the customer. Additionally, this approach helps in averting traffic congestion. Common switching points leading to delayed/dropped traffic are reduced if not altogether eliminated. However, these advantages could be realized only by effective inter-router communication methods for mobility management by call redirection (soft handoff) and MPLS path reconfiguration as the mobile device transitions between cells. The proposed innovation should also be implemented without compromising the quality of service (QOS). In the following subsections, we describe the mechanisms for soft handoff and QOS in the proposed architecture.