ENERGY-EFFICIENT STRATEGIES FOR COOPERATIVE MULTICHANNEL MAC PROTOCOLS
ENERGY-EFFICIENT STRATEGIES FOR COOPERATIVE MULTICHANNEL MAC PROTOCOLS
Distributed Information SHaring (DISH) is a new cooperative approach to designing multichannel MAC protocols. It aids nodes in their decision making processes by compensating for their missing information via information sharing through neighboring nodes. This approach was recently shown to significantly boost the throughput of multichannel MAC protocols. However, a critical issue for ad hoc communication devices, viz. energy efficiency, has yet to be addressed. In this paper, we address this issue by developing simple solutions that reduce the energy consumption without compromising the throughput performance and meanwhile maximize cost efficiency. We propose two energy-efficient strategies: in-situ energy conscious DISH, which uses existing nodes only, and altruistic DISH, which requires additional nodes called altruists. We compare five protocols with respect to these strategies and identify altruistic DISH to be the right choice in general: it 1) conserves 40-80 percent of energy, 2) maintains the throughput advantage, and 3) more than doubles the cost efficiency compared to protocols without this strategy. On the other hand, our study also shows that in-situ energy conscious DISH is suitable only in certain limited scenarios.
Using multiple channels in communication is key to improving the quality of service for wireless networks, and multichannel MAC protocol design has thereby attracted substantial attention from the research community.
Various design approaches have been proposed in the last decade or so, but most of them require either multiple radios or time synchronization. Recently, Luo et al. proposed a distinct approach called Distributed Information SHaring (DISH), which uses a single radio but operates asynchronously.
The authors designed a DISH-based protocol called CAM-MAC , in which neighboring nodes share control information with each sender-receiver pair to facilitate it to choose collision-free channels or to avoid busy receivers.
DISH is essentially a form of node cooperation, but the key difference is that, in traditional cooperation, intermediate nodes help relay data for source and destination nodes, but DISH, on the other hand, only requires control information to be sent. Therefore, the former can be called data-plane cooperation and the latter can be called control-plane cooperation.
We propose two energy-efficient strategies, in-situ energy conscious DISH and ltruistic DISH, to address this issue.
In the in-situ strategy, existing nodes rotate the responsibility of information sharing such that nodes without this responsibility can sleep when idle in order to save power.
In the altruistic strategy, additional nodes called altruists are deployed to take over the responsibility of information sharing so that all the existing nodes can sleep when idle.
A node has a data packet to send but does not know the routing path to the destination, it initiates the route discovery procedure by broadcasting a control packet, called route request (RREQ). When an RREQ reaches the destination, it prepares another control packet, called route reply (RREP), and replies back to the source with the complete route information. Upon receiving an RREP, the source saves the route information in its local memory, called route cache, for later uses. Since nodes move randomly in a MANET, link errors occur and route information that includes a broken link becomes obsolete. When a nod e detects a link error during its data transmission, it sends another control packet, called route error (RERR), to the source and deletes the stale route from its route cache. Overhearing improves the network performance by allowing nodes to collect more route information. Nodes in the vicinity of a transmitter would learn about the path to the destination via overhearing.
Multihop Time Reservation using Adaptive Control for Energy efficiency (MH-TRACE) is a MAC protocol for energy-efficient real-time data communications. A MH-TRACE clustering and medium access for a portion of a distribution of mobile nodes. In MH-TRACE, the network is partitioned into overlapping clusters through a distributed algorithm. Time is organized into cyclic constant duration super frames TSF consisting of several frames. Each cluster head (CH) chooses the least noisy frame to operate within and dynamically changes its frame according to the interference level of the dynamic network. Nodes gain channel access through a dynamically updated and monitored transmission schedule created by the CHs, eliminating packet collisions within the cluster. Collisions with the members of other clusters are also reduced by the CH’s selection of the minimal interference frame. Thus, intercluster interference is not completely eliminated in MH-TRACE due to the limited carrier sensing range of the radios, yet the benefits of the coordination obtained with MH-TRACE (e.g., high throughput, low energy dissipation, and low jitter) are superior to that which can be obtained with a CSMA-type MAC protocol
Power saving in PCF is achieved by the coordination of the AP. Each node operates either in AM or PS mode. With PCF, the AP operates in AM and all other mobile nodes operate in PS mode. The AP periodically sends a beacon for synchronizing mobile nodes in its neighborhood. The beacon includes Traffic Indication Map (TIM), which is a bitmap vector to indicate the traffic and the corresponding receiver. If a node is specified as a receiver in the TIM, it remains awaken to receive a packet during the following data transmission period. It switches off its radio subsystem otherwise.
This section describes the proposed RandomCast protocol. It is designed to improve energy performance by controlling the level of overhearing and forwarding without a significant impact on network performance , the proposed scheme assumes that mobile nodes employ 802.11 PSM and consistently operate in the PS mode. Presents the basic idea of RandomCast and its advantages. Discuss the RandomCast mechanism for unicast and broadcast packets, respectively. Randomization algorithm is described in analyzes the trade-off between energy and the quality of route information in RandomCast.
When a node has a large number of neighbors, there potentially exists a high redundancy. For example, when a node asks for a routing path by sending an RREQ, it is possible that a neighbor offers one. This is one of the most obvious criteria that helps extend the network lifetime: less overhearing (a lower PR) and less rebroadcast (a lower PF ) if remaining battery energy is low. However, it is necessary to take other nodes’ remaining battery energy into consideration in order to achieve a balanced energy consumption
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