Huseyin Haci

Performance study of a wireless mobile ad hoc network with orientation-dependent internode communication scheme

A Petri-net-based simulation model of a wireless mobile ad hoc network is developed and studied. The model covers all the fundamental aspects of behaviour of such a network and uses a novel scheme of orientation-dependent or sector-dependent internode communication, with random states of links. The proposed scheme enables representation of reliability aspects of wireless communication, such as fading effects, interferences, presence of obstacles and weather conditions in a general and rather easy way. The simulation model was implemented in terms of a class of extended Petri nets to explicitly represent parallelism of events and processes in the WLAN as a distributed system. In the simulation, the behaviour of four fundamental performance metrics - packet delivery ratio, average number of hops, relative network traffic and end-to-end delay - were investigated with varying distance of transmission and different combinations of model parameters. Copyright

Novel scheduling for a mixture of real-time and non-real-time traffic

This paper presents a novel scheduling policy for wireless communications where users contain mixed real-time (RT) and non-real-time (nRT) traffic. The proposed policy introduces a novel tradeoff concept in scheduling, where a value of quality of service (QoS) satisfaction can be traded off with the achievable system throughput. Two weighting factors, corresponding to RT and nRT traffic, are introduced in the novel scheduling policy. The proposed policy is evaluated by simulation results. The simulation results show an optimal range of the weights to meet QoS satisfactions.

Performance of Non-orthogonal Multiple Access With a Novel Asynchronous Interference Cancellation Technique

The non-orthogonal multiple access (NOMA) allows one subcarrier to be allocated to more than one user at the same time in an orthogonal frequency division multiplexing (OFDM) system. NOMA is a promising technique to provide high throughput due to frequency reuse within a cell. In this paper, a novel interference cancellation (IC) technique is proposed for asynchronous NOMA systems. The proposed IC technique exploits a triangular pattern to perform the IC from all interfering users for the desired user. The bit error rate and the capacity performance analysis of an uplink NOMA system with the proposed IC technique are presented, along with the comparison to orthogonal frequency division multiple access (OFDMA) systems. The numerical and simulation results show that the NOMA with the proposed asynchronous IC technique outperforms the OFDMA. It is also shown that employing iterative IC provides significant performance gain for NOMA and the number of required iterations depends on the modulation level and the detection method. With hard decision, two iterations are sufficient, and however, with soft decision, two iterations are enough only for low modulation level, and more iterations are desirable for high modulation level.

A Proposal for Dynamic Frequency Sharing in Wireless Networks

Wireless networks are today employed as complementary access technology, implemented on the last hop towards the Internet end-user. The shared media that wireless deployments provide and which is relevant to interconnect multiple users has a limited technical design, as only one device can be served per unit of time, design aspect that limits the potential applicability of wireless in dense environments. This paper proposes and evaluates a novel MAC-layer mechanism that extends current wireless networks with the possibility to perform downstream transmission to multiple devices within a single transmission time-frame, resulting in improved fairness for all devices. The mechanism, which is software-defined, is backward-compatible with current wireless standards and does not require any hardware changes. The solution has been validated in a realistic testbed, and the paper provides details concerning the computational aspects of our solution; a description of the implementation; and results extracted under different realistic scenarios in terms of throughput, packet loss, as well as jitter.

Novel scheduling characteristics for mixture of real-time and non-real-time traffic

This paper presents comprehensive performance analyses of a novel scheduling policy for wireless communications where users have mixed real-time (RT) and non-real-time (nRT) traffic. Also, it introduces novel characteristics to scheduling where the QoS perceived by RT and nRT streams within a mixed traffic system can be differentiated and managed. Performance comparisons with popular proportional fair scheduling policy as well as the convergence analysis are also included.

A Novel Interference Cancellation Technique for Non-Orthogonal Multiple Access (NOMA)

In this paper, a novel interference cancellation (IC) technique is proposed for asynchronous non-orthogonal multiple access (NOMA) systems. The bit error rate (BER) performance of an uplink NOMA system with the proposed IC technique is presented. Numerical and simulation results have shown that NOMA with the proposed asynchronous IC technique outperforms NOMA with a conventional-IC technique for uplink transmissions. It is also shown that employing iterative IC provides significant performance gain in NOMA and the number of required iterations depends on the modulation level and the received power ratio between users.

Performance study of a wireless mobile ad hoc network with orientation-dependent inter-node communication links

A Petri-net-based simulation model of a wireless mobile ad hoc network is studied. The model includes a parameterized mobility model and a novel scheme of orientation-dependent inter-node communication links with random states. In simulation, three fundamental performance metrics — packet delivery rate, average number of hops and relative network traffic — are investigated under different combinations of model parameters.

Cooperative Networking in User-Centric Wireless Networks

Mobile social networking is becoming a new trend allowing users to have instant and real-time access from their devices to any Internet based networking platform. This requirement is not fulfilled by current wireless networks, which provide a limited number of wireless access points with instant Internet access. However, the flexibility of wireless technologies is giving rise to new types of wireless access networks, allowing the Internet to expand in a user-centric way. This new user-centric wireless networking trend aims to mitigate such problems, by allowing sharing of wireless resources for a faster and ubiquitous Internet access. The European project ULOOP—User-centric Wireless Local Loop is investigating new ways of deploying wireless local loops by means of low-cost technologies, where resource sharing is backed up by specific cooperation incentives and mechanisms. This paper aims to introduce the new concept of user-centric networks, an analysis of the most relevant incentive models, and a cooperative networking model to sustain the deployment of low-cost user-centric wireless networks based on cooperation incentives and mechanisms.

Performance study of non-orthogonal multiple access (NOMA) with triangular successive interference cancellation

The non-orthogonal multiple access (NOMA) allows allocating one carrier to more than one user at the same time in one cell. It is a promising technology to provide high throughput due to carrier reuse within a cell. In this paper, a novel interference cancellation (IC) technique is proposed for asynchronous NOMA systems. The proposed IC technique exploits a triangular pattern to perform the IC from all interfering users for the desired user. The bit error rate performance analysis of an uplink NOMA system with the proposed IC technique is presented, along with the comparison to conventional IC technique. The numerical and simulation results show that the NOMA with the proposed asynchronous IC technique outperforms the conventional IC. It is also shown that employing iterative IC provides significant performance gain for NOMA and the number of required iterations depends on the modulation level and the detection method. With hard-decision, two iterations are sufficient, however with soft-decision, two iterations are enough only for low modulation level, and more iterations are desirable for high modulation level.

A Proposal for Elastic Spectrum Management in Wireless Local Area Networks

The last hop of the Internet towards the end-user is mostly supported by wireless technologies and thus interconnects multiple users, that should, ideally, be served simultaneously. The shared media capability of such last hop is, however, underused, asthe principle behind wireless technologies implies that only one user can be served at an instant in time. Aiming at allowing multiuser transmission within a specific time-frame, this technological demonstration goes over a novel wireless extension mechanism explaining how it can be applied to current wireless networks while keeping backward compatibility.