Random Linear Fountain Code with Improved Decoding Success Probability

In this paper we study the problem of increasing the decoding success probability of random linear fountain code over GF(2) for small packet lengths used in delay-intolerant applications such as multimedia streaming. Such code over GF(2) are attractive as they have lower decoding complexity than codes over larger field size, but suffer from high transmission redundancy. In our proposed coding scheme we construct a codeword which is not a linear combination of any codewords previously transmitted to mitigate such transmission redundancy. We then note the observation that the probability of receiving a linearly dependent codeword is highest when the receiver has received k-1 linearly independent codewords. We propose using the BlockACK frame so that the codeword received after k-1 linearly independent codeword is always linearly independent, this reduces the expected redundancy by a factor of three.Comment: This paper appears in: Communications (APCC), 2016 22nd Asia-Pacific Conference o

Throughput Bound of XOR Coded Wireless Multicasting to Three Clients

It is a well-known result that constructing codewords over $GF(2)$ to minimize the number of transmissions for a single-hop wireless multicasting is an NP-complete problem. Linearly independent codewords can be constructed in polynomial time for all the $n$ clients, known as maximum distance separable (MDS) code, when the finite field size $q$ is larger than or equal to the number of clients, $q\geq n$. In this paper we quantify the exact minimum number of transmissions for a multicast network using erasure code when $q=2$ and $n=3$, such that $q<n$. We first show that the use of Markov chain model to derive the minimum number of transmissions for such a network is limited for very small number of input packets. We then use combinatorial approach to derive an upper bound on the exact minimum number of transmissions. Our results show that the difference between the expected number of transmissions using XOR coding and MDS coding is negligible for $n=3$.Comment: This paper appears in the proceedings of 20th IEEE International Workshop on Computer Aided Modelling and Design of Communication Links and Networks (CAMAD), 7-9 September 2015, University of Surrey, Guildford, U

Cooperative Coded Data Dissemination for Wireless Sensor Networks

In this poster paper we present a data dissemination transmission abstraction for over the air programming (OAP) protocol which is fundamentally different from the previous hop by hop transmission protocols. Instead of imposing the greedy requirement that at least one node in the ith hop receives all packets before transmitting packets to the next hop and its neighbours, we take advantage of the spatial diversity and broadcast nature of wireless transmission to adopt a cooperative approach in which node broadcast whatever packets it has received with the expectation that it will recover the lost packets with high probability by overhearing the broadcast transmissions of its neighbours. The use of coded transmissions ensures that this does not lead to the broadcast storm problem. We validate the improved performance our of proposed transmission scheme with respect to the previous state of the art OAP protocols on a proof-of-concept two-hops TelosB wireless sensor network testbed.Comment: This paper appears in: 2016 13th Annual IEEE International Conference on Sensing, Communication, and Networking (SECON), London, 2016, pp. 1-

Collision Codes: Decoding Superimposed BPSK Modulated Wireless Transmissions

The introduction of physical layer network coding gives rise to the concept of turning a collision of transmissions on a wireless channel useful. In the idea of physical layer network coding, two synchronized simultaneous packet transmissions are carefully encoded such that the superimposed transmission can be decoded to produce a packet which is identical to the bitwise binary sum of the two transmitted packets. This paper explores the decoding of superimposed transmission resulted by multiple synchronized simultaneous transmissions. We devise a coding scheme that achieves the identification of individual transmission from the synchronized superimposed transmission. A mathematical proof for the existence of such a coding scheme is given

Cooperative Retransmissions Through Collisions

Interference in wireless networks is one of the key capacity-limiting factors. Recently developed interference-embracing techniques show promising performance on turning collisions into useful transmissions. However, the interference-embracing techniques are hard to apply in practical applications due to their strict requirements. In this paper, we consider utilising the interference-embracing techniques in a common scenario of two interfering sender-receiver pairs. By employing opportunistic listening and analog network coding (ANC), we show that compared to traditional ARQ retransmission, a higher retransmission throughput can be achieved by allowing two interfering senders to cooperatively retransmit selected lost packets at the same time. This simultaneous retransmission is facilitated by a simple handshaking procedure without introducing additional overhead. Simulation results demonstrate the superior performance of the proposed cooperative retransmission.Comment: IEEE ICC 2011, Kyoto, Japan. 5 pages, 5 figures, 2 tables. Analog Network Coding, Retransmission, Access Point, WLAN, interference, collision, capacity, packet los

An Efficient Network Coding based Retransmission Algorithm for Wireless Multicasts

Retransmission based on packet acknowledgement (ACK/NAK) is a fundamental error control technique employed in IEEE 802.11-2007 unicast network. However the 802.11-2007 standard falls short of proposing a reliable MAC-level recovery protocol for multicast frames. In this paper we propose a latency and bandwidth efficient coding algorithm based on the principles of network coding for retransmitting lost packets in a singlehop wireless multicast network and demonstrate its effectiveness over previously proposed network coding based retransmission algorithms.Comment: 5 pages, 5 figure

Maximum Multipath Routing Throughput in Multirate Wireless Mesh Networks

In this paper, we consider the problem of finding the maximum routing throughput between any pair of nodes in an arbitrary multirate wireless mesh network (WMN) using multiple paths. Multipath routing is an efficient technique to maximize routing throughput in WMN, however maximizing multipath routing throughput is a NP-complete problem due to the shared medium for electromagnetic wave transmission in wireless channel, inducing collision-free scheduling as part of the optimization problem. In this work, we first provide problem formulation that incorporates collision-free schedule, and then based on this formulation we design an algorithm with search pruning that jointly optimizes paths and transmission schedule. Though suboptimal, compared to the known optimal single path flow, we demonstrate that an efficient multipath routing scheme can increase the routing throughput by up to 100% for simple WMNs.Comment: This paper has been accepted for publication in IEEE 80th Vehicular Technology Conference, VTC-Fall 201

Achieving reliability for wireless multicast transmission using network coding

Symbol erasure is one the fundamental and inevitable characteristic in data transmission network. This problem exuberates for data transmission on wireless channel due to the shared medium of transmission resulting in packet collisions. Achieving network reliability on wireless channel is even more difficult when data is transmitted to multiple receivers i.e. for wireless multicast transmission. An efficient solution to achieve reliability for wireless multicast transmission is clearly extendable for relatively simpler data transmission models, such as wireline transmission network, wireless unicast transmission, and even on data storage systems to deal with symbol erasures. In this thesis we attempt to address the reliability of wireless multicast transmission at two layers. In the first layer we address the characteristics of the code design to retransmit erased packets. The metrics which we optimize for our code design include throughput performance, decoding delay and encoding and decoding complexities. In the second layer we propose physical layer network coding (PNC) based collision codes to scalably collect packet feedback information from multiple receivers. We further show that PNC based transmission scheme can be harvested for interfering wireless multicast networks to improve the aggregate retransmission throughput performance of the interfering networks. The solutions proposed at each of these two layers complement each other to improve the overall reliability of wireless multicast transmission. An efficient coding decision is dependent on the information about the packet reception status at the receivers. We first develop a scalable scheme to collect packet acknowledgement frames by designing a collision coding scheme whereby all the receivers can simultaneously transmit their acknowledgement frames, resulting in transmission collision. Based on the collided signal, and making use of the collision codes, the transmitter can decode information about the set of receivers which have transmitted their acknowledgement frames. Given the packet feedback information at the transmitter we then propose a coding algorithm, which we call BENEFIT, to design GF(2) linear codes to recover the lost packets. We show that our proposed code has the best throughput and decoding delay performance of any GF(2) linear codes. We then show that by taking advantages of opportunistic listening due to the shared medium of wireless transmission, overlapping transmission range of the interfering transmitters and physical layer network coding scheme, the results of collision codes and BENEFIT coding algorithm, can be extended to interfering multicast networks to improve the aggregate retransmission throughput performance. In the last part of our thesis we design efficient erasure codes where the coding decision is made independently of the feedback information from the receivers, thus completely eliminating the overhead of feedback transmissions from the receivers. The main highlight of these codes, which we call triangular codes, is that triangular codes are the first class of erasure codes which can achieve near-optimal transmission rates, with linear encoding and decoding complexities for finite length input symbol length. We further show that triangular codes outperform all erasure codes with quadratic or subquadratic decoding complexities, including all versions of Luby-Transform codes, Raptor codes, and the standardized versions of Raptor codes, the Raptor 10 and Raptor Q codes.DOCTOR OF PHILOSOPHY (SCE