5 research outputs found
Decoding and File Transfer Delay Balancing in Network Coding Broadcast
Network Coding is a packet encoding technique which has recently been shown
to improve network performance (by reducing delays and increasing throughput)
in broadcast and multicast communications. The cost for such an improvement
comes in the form of increased decoding complexity (and thus delay) at the
receivers end. Before delivering the file to higher layers, the receiver should
first decode those packets. In our work we consider the broadcast transmission
of a large file to N wireless users. The file is segmented into a number of
blocks (each containing K packets - the Coding Window Size). The packets of
each block are encoded using Random Linear Network Coding (RLNC).We obtain the
minimum coding window size so that the completion time of the file transmission
is upper bounded by a used defined delay constraint
Completion Delay of Random Linear Network Coding in Full-Duplex Relay Networks
As the next-generation wireless networks thrive, full-duplex and relaying
techniques are combined to improve the network performance. Random linear
network coding (RLNC) is another popular technique to enhance the efficiency
and reliability in wireless communications. In this paper, in order to explore
the potential of RLNC in full-duplex relay networks, we investigate two
fundamental perfect RLNC schemes and theoretically analyze their completion
delay performance. The first scheme is a straightforward application of
conventional perfect RLNC studied in wireless broadcast, so it involves no
additional process at the relay. Its performance serves as an upper bound among
all perfect RLNC schemes. The other scheme allows sufficiently large buffer and
unconstrained linear coding at the relay. It attains the optimal performance
and serves as a lower bound among all RLNC schemes. For both schemes,
closed-form formulae to characterize the expected completion delay at a single
receiver as well as for the whole system are derived. Numerical results are
also demonstrated to justify the theoretical characterizations, and compare the
two new schemes with the existing one
A protocol design paradigm for rateless fulcrum code
Establecer servicios Multicast eficientes en una red con dispositivos heterog茅neos y bajo los efectos de un canal con efecto de borradura es una de las prioridades actuales en la teor铆a de la codificaci贸n, en particular en Network Coding (NC). Adem谩s, el creciente n煤mero de clientes con dispositivos m贸viles de gran capacidad de procesamiento y la prevalencia de tr谩fico no tolerante al retardo han provocado una demanda de esquemas Multicast sin realimentaci贸n en lo que respecta a la gesti贸n de recursos distribuidos. Las plataformas de comunicaci贸n actuales carecen de un control de codificaci贸n gradual y din谩mico basado en el tipo de datos que se transmiten a nivel de la capa de aplicaci贸n. Este trabajo propone un esquema de transmisi贸n fiable y eficiente basado en una codificaci贸n hibrida compuesta por una codificaci贸n sistem谩tica y codificaci贸n de red lineal aleatoria (RLNC) denominada codificaci贸n Fulcrum. Este esquema h铆brido de codificaci贸n distribuida tipo Rateless permite implementar un sistema adaptativo de gesti贸n de recursos para aumentar la probabilidad de descodificaci贸n durante la recepci贸n de datos en cada nodo receptor de la informaci贸n. En 煤ltima instancia, el esquema propuesto se traduce en un mayor rendimiento de la red y en tiempos de transmisi贸n (RTT) mucho m谩s cortos mediante la implementaci贸n eficiente de una correcci贸n de errores hacia delante (FEC).DoctoradoDoctor en Ingenier铆a de Sistemas y Computaci贸
Throughput and Delay Optimization of Linear Network Coding in Wireless Broadcast
Linear network coding (LNC) is able to achieve the optimal
throughput of packet-level wireless broadcast, where a sender
wishes to broadcast a set of data packets to a set of receivers
within its transmission range through lossy wireless links. But
the price is a large delay in the recovery of individual data
packets due to network decoding, which may undermine all the
benefits of LNC. However, packet decoding delay minimization and
its relation to throughput maximization have not been well
understood in the network coding literature.
Motivated by this fact, in this thesis we present a comprehensive
study on the joint optimization of throughput and average packet
decoding delay (APDD) for LNC in wireless broadcast. To this end,
we reveal the fundamental performance limits of LNC and study the
performance of three major classes of LNC techniques, including
instantly decodable network coding (IDNC), generation-based LNC,
and throughput-optimal LNC (including random linear network
coding (RLNC)).
Various approaches are taken to accomplish the study, including
1) deriving performance bounds, 2) establishing and modelling
optimization problems, 3) studying the hardness of the
optimization problems and their approximation, 4) developing new
optimal and heuristic techniques that take into account practical
concerns such as receiver feedback frequency and computational
complexity.
Key contributions of this thesis include:
- a necessary and sufficient condition for LNC to achieve the
optimal throughput of wireless broadcast;
- the NP-hardness of APDD minimization;
- lower bounds of the expected APDD of LNC under random packet
erasures;
- the APDD-approximation ratio of throughput-optimal LNC, which
has a value of between 4/3 and 2. In particular, the ratio of
RLNC is exactly 2;
- a novel throughput-optimal, APDD-approximation, and
implementation-friendly LNC technique;
- an optimal implementation of strict IDNC that is robust to
packet erasures;
- a novel generation-based LNC technique that generalizes some of
the existing LNC techniques and enables tunable throughput-delay
tradeoffs