• Login
    View Item 
    •   etd@IISc
    • Division of Electrical, Electronics, and Computer Science (EECS)
    • Electrical Communication Engineering (ECE)
    • View Item
    •   etd@IISc
    • Division of Electrical, Electronics, and Computer Science (EECS)
    • Electrical Communication Engineering (ECE)
    • View Item
    JavaScript is disabled for your browser. Some features of this site may not work without it.

    Cooperative Communication In Store And Forward Wireless Networks Using Rateless Codes

    View/Open
    G24470.pdf (653.2Kb)
    Date
    2013-08-30
    Author
    Bansal, Gaurav
    Metadata
    Show full item record
    Abstract
    In this thesis, we consider a cooperative relay-assisted communication system that uses rateless codes. When multiple relays are present, the relay with the highest channel gain to the source is the first to successfully decode a message from the source and forward it to the destination. Thus, the unique properties of rateless codes ensure that both rate adaptation and relay selection occur without the transmitting source or relays acquiring instantaneous channel knowledge. We show that in such cooperative systems, buffering messages at relays significantly increases throughput. We develop a novel analysis of these systems that combines the communication-theoretic aspects of cooperation over fading channels with the queuing-theoretic aspects associated with buffering. Closed-form expressions are derived for the throughput and end-to-end delay for the general case in which the channels between various nodes are not statistically identical. Results are also shown for the benchmark system that does not buffer messages. Though relay selection combined with buffering of messages at the relays substantially increases the throughput of a cooperative network, it also increases the end-to-end delays due to the additional queuing delays at the relay nodes. In order to overcome this, we propose a novel method that exploits a unique property of rateless codes that enables a receiver to decode a message from non-contiguous and unordered portions of the received signal. In it, each relay, depending on its queue length, ignores its received coded bits with a given probability. We show that this substantially reduces the end-to-end delays while retaining almost all of the throughput gain achieved by buffering. In effect, the method increases the odds that the message is first decoded by a relay with a smaller queue. Thus, the queuing load is balanced across the relays and traded off with transmission times. We derive conditions for the stability of this system when the various channels undergo fading. Despite encountering analytically intractable G/GI/1 queues in our system, we also gain insights about the method by analyzing a similar system with a simpler model for the relay-to-destination transmission times. Next we combine the single relay selection scheme at the source with physical layer power control at the relays (due to the diversity provided by the rateless codes, power control at the source is not needed). We derive an optimal power control policy that minimizes the relay to destination transmission time. Due to its computational and implementation complexity, we develop another heuristic easily implementable near optimal policy. In this policy, power allocated turns out to be inversely proportional to the square root of channel gain. We also see that this policy performs better than the channel inversion policy. Our power control solution substantially decreases the mean end-to-end delays with a marginal increase in throughput also. Finally, we combine bit dropping with power control at the relays which further improves the system performance.
    URI
    https://etd.iisc.ac.in/handle/2005/2225
    Collections
    • Electrical Communication Engineering (ECE) [398]

    Related items

    Showing items related by title, author, creator and subject.

    • Biophysical Studies On The Plastic And Cooperative Properties Of Single Voltage Gated Na+ And Leak K+ Ion Channels 

      Nayak, Tapan Kumar (2011-03-08)
      Ion channels are fundamental molecules in the nervous system that catalyze the flux of ions across the cell membrane. There are mounting evidences suggesting that the kinetic properties of ion channels undergo activity-dependent ...
    • Social Organisation And Cooperation In Genetically Mixed Colonies Of The Primitively Eusocial Wasp, Ropalidia Marginata 

      Arathi, H S (Indian Institute of Science, 2005-08-05)
      Altruism in its extreme form is seen in social insects where most individuals give up their own reproduction and work to rear the offspring of their queen. The origin and evolution of such sterile worker castes remains a ...
    • Fast, Scalable, Contention-Based Algorithms for Multi-Node Selection in OFDMA and Cooperative Wireless Systems 

      Karthik, A (2018-04-23)
      Opportunistic selection algorithms have grown in importance as next generation wireless systems strive towards higher data rates and spectral efficiencies. For example, in orthogonal frequency division multiple access(OFDMA), ...

    etd@IISc is a joint service of SERC & J R D Tata Memorial (JRDTML) Library || Powered by DSpace software || DuraSpace
    Contact Us | Send Feedback | Thesis Templates
    Theme by 
    Atmire NV
     

     

    Browse

    All of etd@IIScCommunities & CollectionsTitlesAuthorsAdvisorsSubjectsBy Thesis Submission DateThis CollectionTitlesAuthorsAdvisorsSubjectsBy Thesis Submission Date

    My Account

    LoginRegister

    etd@IISc is a joint service of SERC & J R D Tata Memorial (JRDTML) Library || Powered by DSpace software || DuraSpace
    Contact Us | Send Feedback | Thesis Templates
    Theme by 
    Atmire NV