Parallel Opportunistic Routing in Wireless Networks

We study benefits of opportunistic routing in a large wireless ad hoc network by examining how the power, delay, and total throughput scale as the number of source- destination pairs increases up to the operating maximum. Our opportunistic routing is novel in a sense that it is massively parallel, i.e., it is performed by many nodes simultaneously to maximize the opportunistic gain while controlling the inter-user interference. The scaling behavior of conventional multi-hop transmission that does not employ opportunistic routing is also examined for comparison. Our results indicate that our opportunistic routing can exhibit a net improvement in overall power--delay trade-off over the conventional routing by providing up to a logarithmic boost in the scaling law. Such a gain is possible since the receivers can tolerate more interference due to the increased received signal power provided by the multi-user diversity gain, which means that having more simultaneous transmissions is possible.Comment: 18 pages, 7 figures, Under Review for Possible Publication in IEEE Transactions on Information Theor

Can One Achieve Multiuser Diversity in Uplink Multi-Cell Networks?

We introduce a distributed opportunistic scheduling (DOS) strategy, based on two pre-determined thresholds, for uplink $K$-cell networks with time-invariant channel coefficients. Each base station (BS) opportunistically selects a mobile station (MS) who has a large signal strength of the desired channel link among a set of MSs generating a sufficiently small interference to other BSs. Then, performance on the achievable throughput scaling law is analyzed. As our main result, it is shown that the achievable sum-rate scales as $K\log(\text{SNR}\log N)$ in a high signal-to-noise ratio (SNR) regime, if the total number of users in a cell, $N$, scales faster than $\text{SNR}^{\frac{K-1}{1-\epsilon}}$ for a constant $\epsilon\in(0,1)$. This result indicates that the proposed scheme achieves the multiuser diversity gain as well as the degrees-of-freedom gain even under multi-cell environments. Simulation results show that the DOS provides a better sum-rate throughput over conventional schemes.Comment: 11 pages, 3 figures, 2 tables, to appear in IEEE Transactions on Communication

Optimal Multiuser Diversity in Multi-Cell MIMO Uplink Networks: User Scaling Law and Beamforming Design

We introduce a distributed protocol to achieve multiuser diversity in a multicell multiple-input multiple-output (MIMO) uplink network, referred to as a MIMO interfering multiple-access channel (IMAC). Assuming both no information exchange among base stations (BS) and local channel state information at the transmitters for the MIMO IMAC, we propose a joint beamforming and user scheduling protocol, and then show that the proposed protocol can achieve the optimal multiuser diversity gain, i.e., KM log (SNR log N), as long as the number of mobile stations (MSs) in a cell, N, scales faster than SNRKM-L/1-epsilon for a small constant epsilon > 0, where M, L, K, and SNR denote the number of receive antennas at each BS, the number of transmit antennas at each MS, the number of cells, and the signal-to-noise ratio, respectively. Our result indicates that multiuser diversity can be achieved in the presence of intra-cell and inter-cell interference even in a distributed fashion. As a result, vital information on how to design distributed algorithms in interference-limited cellular environments is provided

Multi-hop Route Discovery Using Opportunistic Routing for Wireless Sensor Networks

In wireless sensor networks multi-hop routing is often used because of the limited transmission range of sensor nodes. Opportunistic Routing is a multi-hop routing for wireless sensor networks. In this routing, the neighbors of sender node overhear the transmission and f``orm multiple hops from source to the destination for transfer of information. The neighbor nodes set participating in the routing are included in the forwarder list in the order of priority. The node with highest priority is allowed to forward the packet it hears. A new protocol by Energy Efficient Selective Opportunistic Routing (EESOR), is implemented in this paper that reduces the size of forwarder list by applying a condition that the forwarding node is nearer to the destination. The path followed by acknowledgment packet follows opportunistic routing, assuring reliability of transmission and energy balancing. NS2 is the simulator used to implement the algorithm and results of simulation show that proposed EESOR protocol performs better than existing Energy Efficient Opportunistic Routing (EEOR) protocol with respect to parameters End-to-End Delay, Throughput, Routing Overhead and Network Lifetime

EESOR: Energy efficient selective opportunistic routing in wireless sensor networks

Opportunistic Routing in wireless sensor networks is a multi-hop routing. In this routing neighbors of a node overhear the transmission and form multiple hops from source to the destination for transfer of information. The set of neighbor nodes participating in the routing are included in the forwarder list in the order of priority. A node with highest priority is allowed to forward the packet it hears. This paper implements Energy Efficient Selective Opportunistic Routing (EESOR), reduces the size of forwarder list by applying a condition that the forwarding node is nearer to the destination. The path followed by acknowledgment packet follows opportunistic routing, assuring reliability of transmission and energy balancing. The simulated results obtained in NS2 simulator show that proposed EESOR protocol performs better than existing Energy Efficient Opportunistic Routing (EEOR) protocol in terms of average End-to