Proteus: Multiflow Diversity Routing for Wireless Networks with Cooperative Transmissions
In this paper, we consider the use of cooperative transmissions in multihop wireless networks to achieve Virtual Multiple Input Single Output (VMISO) links. Specifically, we investigate how the physical layer VMISO benefits translate into network level performance improvements. We show that the improvements are nontrivial (15 to 300 percent depending on the node density) but rely on two crucial algorithmic decisions: the number of cooperating transmitters for each link; and the cooperation strategy used by the transmitters. We explore the tradeoffs in making routing decisions using analytical models and derive the key routing considerations. Finally, we present Proteus, an adaptive diversity routing protocol that includes algorithmic solutions to the above two decision problems and leverages VMISO links in multihop wireless network to achieve performance improvements. We evaluate Proteus using NS2-based simulations with an enhanced physical layer model that accurately captures the effect of VMISO transmissions
PROJECT OUTPUT VIDEO: (Click the below link to see the project output video):
In a VMISO system, multiple transmitters transmit encoded versions of the same signal so that the error performance at the receiver is improved significantly compared to a traditional Single Input Single Output (SISO) system. In this work, we consider a specific instance of VMISO communication, where all transmitters of the array transmit with the same fixed power. In such systems, the cooperation gain directly leads to a smaller SNR requirement to achieve the same error performance. The gain in SNR in turn can be used to either increase the data rate by the use of higher order modulations or to increase communication range, thereby improving communication performance in the wireless channel. Although there are several challenges to realizing the potential of VMISO communications, the scope of this paper is restricted to routing.
DISADVANTAGES OF EXISTING SYSTEM:
First, of the different virtual array approaches, VMISO requires the lowest coordination effort because it can leverage the broadcast property of the wireless channel to distribute information to the cooperating transmitters with a single transmission. This is unlike VSIMO or VMIMO, where multiple information exchanges are required at the receiver to decode information.
Second, although VMISO allows improved data rates, the coordination overhead and complexity of channel state information and processing are significant challenges in VMIMO which do not affect VMISO.
Although there are several challenges to realizing the potential of VMISO communications, the scope of this paper is restricted to routing. In this context, we first investigate the benefits achievable when using VMISO in a multihop wireless network. While there have been several related works that discuss how cooperative diversity can improve performance at the physical layer, the higher layer benefits of cooperative diversity have been explored only by a few related works. More importantly none of the related works identify the routing considerations in a wireless network with multiple active flows and using cooperative transmissions. Using a combination of theoretical analysis, simulations and specific examples with arbitrary topologies, we study how physical layer benefits of cooperative diversity translate to network level performance metrics. Our studies reveal that the network benefits of using VMISO links are nontrivial. We then identify two important decisions that influence the achievable benefits in a multihop wireless network that uses VMISO: the choice of the number of cooperating transmitters such that the diversity gain and interference tradeoff is appropriately leveraged; and the choice of the cooperation strategy such that the diversity gain is appropriately used for either an increase in the range or the rate of the links or both. Finally, we propose centralized and distributed versions of a diversity routing protocol that includes algorithms for optimally arriving at both of the above decisions.
ADVANTAGES OF PROPOSED SYSTEM:
- We highlight that the joint adaptation of rate and range becomes especially important for VMISO rather than MIMO/MISO due to the larger diversity gains obtainable with VMISO.
- We show that a simple approach of optimizing the throughput of links followed by optimizing the range can greatly reduce the aggregate throughput of flows compared to jointly optimizing the link rates and the hop distances.
- We propose an adaptive clustering algorithm that dynamically adjusts the cluster size for each flow in the network.
- We also identify several approaches for adapting the rate, range, and cluster size and establish the limitations of each of them.
ü Processor – Pentium –IV
ü Speed – 1.1 Ghz
ü RAM – 512 MB(min)
ü Hard Disk – 40 GB
ü Key Board – Standard Windows Keyboard
ü Mouse – Two or Three Button Mouse
ü Monitor – LCD/LED
v Operating System : LINUX
v Tool : Network Simulator-2
v Front End : OTCL (Object Oriented Tool Command Language)
Sriram Lakshmanan and Raghupathy Sivakumar “Proteus: Multiflow Diversity Routing for Wireless Networks with Cooperative Transmissions”, IEEE TRANSACTIONS ON MOBILE COMPUTING, VOL. 12, NO. 6, JUNE 2013.