Energy-Efficient Protocol for Cooperative Networks
A B S T R A C T
In cooperative networks, transmitting and receiving nodes recruit neighboring nodes to assist in communication. We model a cooperative transmission link in wireless networks as a transmitter cluster and a receiver cluster. We then propose a cooperative communication protocol for establishment of these clusters and for cooperative transmission of data. We derive the upper bound of the capacity of the protocol, and we analyze the end-to-end robustness of the protocol to data-packet loss, along with the tradeoff between energy consumption and error rate.
The analysis results are used to compare the energy savings and the end-to-end robustness of our protocol with two non-cooperative schemes, as well as to another cooperative protocol published in the technical literature. The comparison results show that, when nodes are positioned on a grid, there is a reduction in the probability of packet delivery failure by two orders of magnitude for the values of parameters considered. Up to 80% in energy savings can be achieved for a grid topology, while for random node placement our cooperative protocol can save up to 40% in energy consumption relative to the other protocols. The reduction in error rate and the energy savings translate into increased lifetime of cooperative sensor networks.
Two energy-efficient approximation algorithms are presented for finding a cooperative route in wireless networks. The two algorithms for finding one cooperative route are designed such that each hop consists of multiple sender nodes to one receiver node. Existing methods focus on MAC layer design for networks with cooperative transmission. When no acknowledgement is received from the destination after timeout, the cooperative nodes, which correctly received the data, retransmit it. Only one cooperative node retransmits at any time, and the other cooperative nodes flush their copy once they hear the retransmission.
In the multiple-input–multiple-output (MIMO) systems, each node is equipped with multiple antennas. Information is transmitted from the sender node by multiple antennas and received by multiple antennas at the receiver node. The close proximity of the antennas at the transmitting nodes and of the antennas at the receiving nodes makes synchronization easier to implement. The ability of nodes to sense the carrier and to measure the interference level can be used to decide on the number of antennas that are employed for transmission.
Existing methods focus on MAC layer design for networks with cooperative transmission. When no acknowledgement is received from the destination after timeout, the cooperative nodes, which correctly received the data, retransmit it. Only one cooperative node retransmits at any time
In this project we propose a cooperative communication model with multiple nodes on both ends of a hop and with each data packet being transmitted only once per hop. In our model of cooperative transmission, every node on the path from the source node to the destination node becomes a cluster head, with the task of recruiting other nodes in its neighborhood and coordinating their transmissions. Consequently, the classical route from a source node to a sink node is replaced with a multi-hop cooperative path, and the classical point-to-point communication is replaced with many-to-many cooperative communication. The path can then be described as “having a width,” where the “width” of a path at a particular hop is determined by the number of nodes on each end of a hop.
Every node in the receiving cluster receives from every node in the sending cluster. Sending nodes are synchronized, and the power level of the received signal at a receiving node is the sum of all the signal powers coming from all the sender nodes. This reduces the likelihood of a packet being received in error. We assume that some mechanism for error detection is incorporated into the packet format, so a node that does not receive a packet correctly will not transmit on the next hop in the path. Our cooperative transmission protocol consists of two phases.
In the routing phase, the initial path between the source and the sink nodes is discovered as an underlying “one-node-thick” path. Then, the path undergoes a thickening process in the “recruiting-and-transmitting” phase. In this phase, the nodes on the initial path become cluster heads, which recruit additional adjacent nodes from their neighborhood.
1. Recruiting, Transmitting & receiving:
Our cooperative transmission protocol consists of two phases. In the routing phase, the initial path between the source and the sink nodes is discovered as an underlying “one-node-thick” path. Then, the path undergoes a thickening process in the “recruiting-and-transmitting” phase. In this phase, the nodes on the initial path become cluster heads, which recruit additional adjacent nodes from their neighborhood.
Recruiting is done dynamically and per packet as the packet traverses the path. When a packet is received by a cluster head of the receiving cluster, the cluster head initiates the recruiting by the next node on the “one-node-thick” path. Once this recruiting is completed and the receiving cluster is established, the packet is transmitted from the sending cluster to the newly established receiving cluster.
2. Route Construction:
Upon receiving the CL packet from node 5, node 2 sends a confirm (CF) packet to the nodes in its sending cluster (nodes 1 and 3) to synchronize their transmission of the data packet. The CF packet contains the waiting-time-to-send and the transmission power level. The transmission power level is the total transmission power (a protocol-selectable parameter) divided by the number of the nodes in the sending cluster. In the case of our example, the value of is divided by 3 (nodes 1–3 are cooperating in sending). After the waiting-time-to-send expires, sending cluster nodes 1–3 send the data packet to the receiving cluster nodes
3. Data transmission using CANs:
The capacity of the CAN protocol degrades with an increase in the transmission range, as a transmission on one hop blocks a large number of nodes from transmitting other packets, and hence the network can only carry lower load. In the CAN protocol, failure to receive a packet results in a large reduction in the success probability on the next hop. The disjoint-paths scheme has larger energy consumption, as demonstrated in, which shows the effect of the transmission range on the total energy consumption.
Here, we sum the energy consumption for all packets transmitted (control and data packets). Our cooperative transmission protocol saves between 6% and 20% of the energy consumption compared to the CAN protocol and between 10% and 40% of the energy consumption compared to the disjoint-paths scheme. As the transmission range increases, the contention increases and the noise power increases. This increases the energy consumption. The elevated contention increases the retransmission of control and data packets, which, in turn, increases the total energy consumption.
4. Message details with Route paths:
The work in proposes and evaluates the performance of a cross-layer framework that uses virtual multiple- input–single-output (MISO) links for MANET and shares some similarity with our paper. However, there are some major differences between the two works. On the physical layer, the architecture of is based on “virtual MISO,” which is also referred to in as “virtual antenna array.” As pointed out in that paper, “nodes simultaneously transmit and/or jointly receive appropriately encoded signals.”
This model is totally different from our model, where we use MISO system with orthogonal transmissions. On the MAC layer, relies on the knowledge of the neighbors to select the cooperating nodes. To achieve this, assumes that the list of neighbors is obtained by the HELLO messages of the routing protocol.
The below links contains abstract, base paper, screen shots, UML diagrams, references, documentation, power-point presentation and source code of Energy-Efficient Protocol for Cooperative Networks.