Joint Cooperative Shared Relaying and Multipoint Coordination for Network MIMO in 3GPP LTE-Advanced Multihop Cellular Networks

Abstract

LTE-Advanced (Parkvall et al., 2011; 3GPP TR36.814) is the successor of LTE (Long Term Evolution), which is specified by the Third Generation Partnership Project (3GPP). LTEAdvanced can provide downlink and uplink peak rates up to 1 Gb/s and 500 Mb/s, respectively, in 100 MHz of bandwidth. Similar to its predecessor, LTE-Advanced is an Orthogonal Frequency Division Multiplexing (OFDM)-based radio access technology, with conventional OFDM on the downlink and Discrete Fourier Transform Spread OFDM (DFTSOFDM) in the uplink. In addition, LTE-Advanced includes several new key technological components, namely carrier aggregation, enhanced MIMO (Multiple-Input Multiple Output), Coordinated MultiPoint transmission and reception (CoMP), and relaying. In this chapter, we focus on the CoMP component and the relaying component. CoMP is a means of coordinating the transmission and reception of data from/to a single mobile terminal using several geographically distributed base stations. Essentially, CoMP eliminates inter-cell interference by effectively having the multiple base stations act as a single transceiver. CoMP is especially effective for improving data rates of cell-edge mobile terminals where performance is degraded due to inter-cell interference since LTEAdvanced uses full-frequency reuse. Relaying is employed as a low-cost solution to enhance cell-coverage and -capacity. With relaying, the mobile terminal communicates with the base station via a relay node that is wirelessly connected to the base station using the same radio resources as for the mobile terminal that is directly connected to the base station. An LTE-Advanced relay node is divided into a transparent type and a nontransparent type. The main difference between the two types is in the amount of functionality and intelligence included in the relay node. A non-transparent relay node has more functionality and intelligence than a transparent one. This means it is also costlier. The simplest and the cheapest transparent relay is known as Amplify and Forward (AF). The aim of this chapter is to leverage and combine the benefits of CoMP and relaying in order to improve the performance of cell-edge users, which is severely degraded due intercell interference. The joint relaying and CoMP technique can yield performance gains