Cooperative Communication

Performance Metrics (Cooperative Diversity)

Consider a point-to-point channel as in Figure 2.2 and suppose the coded modulation rate is R (see Section 2.2.3). Let 7 be the average SNR at the receiver and let I(7) be the mutual information between the channel inputs and outputs. Observe that I(7) is a random variable that depends on the fading coefficients. We […]

System Model (Cooperative Diversity)

We study the performance of cooperative protocols for the network shown in Figure 5.2. The network outputs are for i = 1,2,… ,n. The transmitting nodes have half-duplex constraints. The noise variables Zu,i, u = 1,2,3, i = 1,2,…,n, and channel gains Huv are the usual complex, Gaussian random variables (see Section 3.2 and (3.3a) […]

Cooperative Strategies for High SNR (Cooperative Diversity)

We consider two classes of strategies by distinguishing whether the sources transmit at the same time and in the same frequency band or not.1 Strategies for which the sources do not interfere are called orthogonal strategies. Such schemes are meant to achieve high diversity gains rather than high rates [112], although orthogonal strategies are good […]

Relaying Strategies for Low SNR (Cooperative Diversity)

We next turn our attention to low SNR. However, for simplicity we focus on the RC rather than the network of Figure 5.2. We again consider TDM and orthogonal cooperative strategies: the source transmits half the time, and the relay listens and talks half the time.2 However, we will let the source transmit for a […]

Multiplexing Gain for Wireless Networks (Cooperative Diversity)

The results presented so far considered a single destination. Consider now a 2 x 2 wireless network with two source nodes and two sink nodes (see Figure 5.5). Source u, u = 1,2, wishes to send a message to sink node u + 2. We pose the question: can one achieve MIMO multiplexing gains in […]

Other Models and Methods (Cooperative Diversity)

A variety of models has been considered to study cooperative capacity and diversity. For example, the cognitive radio channel shown in Figure 3.9 lets the source nodes cooperate by having one of the nodes aware of the message of the other node. The capacity region of this channel is known in some cases [89, 189]. […]

Wireless Networking Protocols

Introduction We have observed that cooperative networks enable a more complex set of interactions between the physical, link, and network layers. Transmissions are not point-to-point and routing is not store-and-forward. We need to distinguish between a message that an application wishes to communicate and the data packets that are transmitted in the network. At the […]

Wireless Cooperation Issues (Wireless Networking Protocols)

Networking traditionally defines the sequence of intermediate node transmissions as a path or route. One way to think about cooperative communication methods is to view a set of n nodes participating in delivering packets from a source to a destination as a multi-terminal link. We refer to this generalization as a cooperative link, or simply […]

Networking Mechanisms (Wireless Networking Protocols)

We have identified the primary tasks of cooperative networks, namely message decoding, cooperative link establishment, and cooperative routing. These tasks must be completed by peer protocols at the link layer, MAC sublayer, and network layer. In any wireless network, signaling channels are defined to facilitate these protocols. For example, a packet header that identifies the […]

Conventional PHY Layer Architecture (Wireless Networking Protocols)

A conventional architecture for the physical and link layers has a demodulator and decoder, as shown in Figure 6.1. Packet reception occurs in the DEMOD module that demodulates, samples, and puts out quantized real- or complex-valued soft symbols. These symbols are fed to the DECODER module to produce a data packet. If the packet has […]