Future WiMAX relay stations have you hop until you drop

The IEEE 802.16's Relay Task Group is developing a multihop relay specification to extend WiMAX base station reach and coverage.

Base stations come in multiple shapes and coverage sizes, including macro, micro, pico and femto cell. The primary difference between these is the size of coverage. Macro cell base stations offer the greatest range, though they also have the most coverage dead zones. Pico and femto cell base stations are used to fill in coverage gaps and establish coverage in buildings where the larger base station signals cannot penetrate. A significant side-effect of placing many base stations in a region is that each one needs a dedicated broadband backhaul connection.

In 2006, the IEEE approved a project, called P802.16j (802.16j), for a mobile multihop relay (MMR) specification to extend base station reach and coverage without the backhaul requirement. The MMR base station (BS) provides the primary area of coverage in the diagram. It also has a backhaul connection, such as leased copper or fiber optics. The relay station (RS) extends the base station coverage. A mobile subscriber station (MS) can connect to a base station, an MMR base station or a relay station.

The relay architecture should not be confused with a mesh topology. Mesh utilizes all of the subscriber stations to form the paths of the network. The relay approach uses only infrastructure equipment to extend the reach of the network without dependency on subscriber devices. Advantages of the MMR approach are a less complex design and construction than typical base stations, lower total system cost, and enabling rapid deployment. Multiple hops between a mobile station and base station are supported. Existing 802.16e-2005 base stations should be software upgradeable to the MMR capability.

Operators will determine future base station placement without worrying if a backhaul connection is present or affordable. Monthly leased line backhaul costs are minimized. Service providers in emerging countries will overcome unsatisfactory wired broadband infrastructure. End-users of the MMR-enabled network will benefit from improved mobile broadband coverage.

By Jeff Orr, ORR Technology

Friday, February 15, 2008 in Applications  | Permalink |  Comments (0)