Cooperative Communication

Source and Destination Models (Network Models)

The previous sections describe device (node) and channel (edge) models. A communication network also has sources and sinks, and we will consider bit sources where every bit is uniformly distributed and is independent of all other message bits. We thereby implicitly assume that multimedia signals, such as voice or video, are compressed to bit streams, […]

Network Capacity (Network Models)

In the context of multi-node networks, we would like to define capacity in a similar manner as in Section 2.2.1 for a DMC and AWGN channel. Suppose there are M sources and source m puts out message Wm with bits, m = 1,2,…, M. The messages are assumed to be independent. For convenience, we introduce […]

Wireline Strategies (Cooperative Strategies and Rates)

This topic introduces several cooperative strategies. We will consider primarily wireless networks, and we further consider either no fading or fast fading. Slow fading channels will be treated in topic 5. For all cases, we consider only "CSIR, No CSIT" models where each node knows the channel gains between itself and the nodes with which […]

Wireless Strategies Part 1 (Cooperative Strategies and Rates)

The previous section shows how network coding combines raw bits or packets at the network layer to improve rates. More generally, cooperative coding combines symbols at the physical and higher layers to produce new symbols. We consider several types of cooperative coding strategies, including (1) amplify-and-forward (AF) (2) classic multi-hop (3) compress-and-forward (CF) (4) decode-and-forward […]

Wireless Strategies Part 2 (Cooperative Strategies and Rates)

Decode-and-Forward Decode-and-forward is a block-transmission strategy that has the block structure shown in Figure 4.12 [33, 106]. There are two code books: The source uses block Markov encoding, i.e., the encoding has one block memory in that the source codeword in block b is . The idea is that the relay knows wb—1 and decodes […]

Wireless Strategies Part 3 (Cooperative Strategies and Rates)

Decode-and-Forward with Network Coding Decode-and-forward can be combined with network coding in several ways, and we develop such strategies for two classes of wireless channels in this and the next section. Consider first the network shown in Figure 4.20 and suppose the channels are defined by where the Huv and Zu are the usual complex, […]

Half-Duplex Strategies and Mode Modulation (Cooperative Strategies and Rates)

The information theory developed in the previous sections applies to both full-duplex and half-duplex devices [106]. In this section, we consider the theory in more detail for half-duplex devices. For example, we demonstrate that half-duplex nodes can transmit data by modulating their "listen" to "talk" modes [103]. However, despite their fundamental nature, one might not […]

Multi-Antenna Relaying (Cooperative Strategies and Rates)

The information theory developed above applies to devices equipped with multiple antennas in a similar fashion as in Section 2.2.5. We again make the channel inputs and outputs vectors and write whereare complex column vectors of length nu, and Huv is a complexfading matrix. Thehave independent, Gaussian, variance N entries with the usual form. The […]

Code Design for Relaying (Cooperative Strategies and Rates)

We outline a code construction for half-duplex relays and for the Rayleigh fading channels of Section 4.4. The design is based on a point-to-point multi-antenna strategy known as Diagonal Bell Labs Layered Space-Time (D-BLAST) [53]. Other code constructions for relay channels are described in, e.g., [83, 200] (convolutional codes), [111] (space-time codes), [198] (turbo codes), […]

Cooperative Diversity

Introduction The previous topic examined cooperative strategies when no fading or fast fading is present. The main performance metric was rate because long codes can average out the effects of noise and fading and can make the error probability approach zero. In this topic, we consider another extreme, namely, slow fading where the channel gains […]