Increasing the throughput in multi-hop wireless networks by using spatial multiplexing

Proposed data rates for future mobile communication systems of 100 Mbps and more require large transmission bandwidths. As the bandwidth in the 2 GHz range is very limited, the future systems are likely to be allocated in the wireless LAN bands around 5 GHz or at even higher frequencies. Rising the carrier frequencies results in a higher path loss which would lead to a dense mesh of access points (base stations) to guarantee coverage. To avoid the high number of access points, multi hop concepts such as the wireless media system (WMS) are proposed to extend the range of the access points. In a typical multi-hop scenario the data is routed from an access point (AP) over one or more relays to the mobile station. The relays do not require a connection to the core network. Therefore, the infrastructure costs are lower. These concepts might use fixed or mobile wireless relays (FWRs) to extend the range of the AP as this guarantees a certain coverage. If the WMS uses relaying in the time domain, there is a reduction of the throughput for each hop due to idle times. This reduction in throughput is avoided by the use of spatial multiplexing via smart antennas. This is due to the fact that a relaying scheme based on spatial multiplexing (RSM) can handle several connections to spatially separated locations at the same time.