Jaber Mohammad Borran

Cell Association and Interference Coordination in Heterogeneous LTE-A Cellular Networks

Embedding pico/femto base-stations and relay nodes in a macro-cellular network is a promising method for achieving substantial gains in coverage and capacity compared to macro-only networks. These new types of base-stations can operate on the same wireless channel as the macro-cellular network, providing higher spatial reuse via cell splitting. However, these base-stations are deployed in an unplanned manner, can have very different transmit powers, and may not have traffic aggregation among many users. This could potentially result in much higher interference magnitude and variability. Hence, such deployments require the use of innovative cell association and inter-cell interference coordination techniques in order to realize the promised capacity and coverage gains. In this paper, we describe new paradigms for design and operation of such heterogeneous cellular networks. Specifically, we focus on cell splitting, range expansion, semi-static resource negotiation on third-party backhaul connections, and fast dynamic interference management for QoS via over-the-air signaling. Notably, our methodologies and algorithms are simple, lightweight, and incur extremely low overhead. Numerical studies show that they provide large gains over currently used methods for cellular networks.

Interference Management and Handoff Techniques in Ultra Mobile Broadband Communication Systems

Wireless communications of the next generation rely on large bandwidths and orthogonal frequency division multiple access (OFDMA) techniques to achieve high data rates. In a OFDMA-based wireless wide area network (WWAN), e.g., a cellular network, interference management and handoff are keys to the system performance, such as capacity, coverage, and stability. This paper introduces novel interference management schemes for use in a OFDMA cellular communication system that include dynamic fractional frequency reuse scheme and other cell interference based power control for interference control and avoidance and handoff schemes that employs disjoint links and beacons in a OFDMA cellular communication system.

Distributed Interference Management and Scheduling in LTE-A Femto Networks

We design novel mechanisms and algorithms for fast, simple, and distributed interference management and scheduling in wireless femto networks via exchange of information over-the-air (OTA). We focus on the Long Term Evolution (LTE) of the 3GPP standard and on the downlink; we leverage the existing signalling and delineate additional signals that need to be introduced in the standard. Key aspects of our work include: (1) our design involves only one round of exchange of very few bits of information in each time slot (of the order of 1 ms) resulting in a very low control overhead, (2) our algorithm is a heuristic derived from the maximum weight scheduling algorithm for a realistic interference model (as opposed to an abstract

Impact of Coordination Delay on Distributed Scheduling in LTE-A Femtocell Networks

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Interference management and handoff techniques

-hop interference model), and (3) our framework allows for an easy control of fairness for best effort flows, control of delay tails for delay sensitive QoS flows, and relative prioritization between best effort and QoS flows. The performance of the mechanisms and algorithms is validated using system simulations based on 3GPP evaluation methodology.

Interference coordination for peer-to-peer (p2p) communication and wide area network (wan) communication

We consider wireless femtocell networks where scheduling of transmissions is coordinated across multiple cells to mitigate interference and deliver fairness and quality of service (QoS). Coordination across multiple cells entails (i)~exchange of (serving and interfering) channel information and traffic priority (which is a function of packet delays, average rate, queue length), and (ii)~signalling of transmission powers over pilots so that neighboring cells can determine the expected SINR to pick the right modulation and coding scheme. Such an exchange entails delay in coordination resulting in scheduling decisions made on the basis of stale information received from other cells. In this paper, we study aspects of practical signalling and algorithm design to account for such coordination delay and study its impact. When the coordination across cells is done over a high latency backhaul, we design a hybrid signalling mechanism where minimal amount of additional over-the-air (OTA) signalling enhancement can lead to tremendous performance improvement. We demonstrate the benefits of our algorithms and mechanisms via comparison to a centralized scheduler and reuse one scheme using system simulations based on 3GPP evaluation methodology.

Enhanced block-request streaming system for handling low-latency streaming

Intersector interference management is crucial in universal frequency reuse systems like OFDMA. In this article, we described advanced interference management techniques for future OFDMA communication systems. Such techniques include dynamic frequency reuse, intersector interference-based power control, and effective intersector handoff using disjoint FL and RL and beacon signaling. Dynamic frequency reuse provides flexible tradeoff between overall capacity and sector edge capacity, resulting in higher sector edge performance and smoother handoff while still keeping the reuse factor close to one. Dynamic frequency reuse scheduling dynamically allocates subcarriers to users for efficient interference control. This article also describes how effective power control can be utilized to tightly manage intersector interference for maintaining system stability in a universal frequency reuse OFDMA system. Transmit power of different ATs is shaped according to the amount of interference they cause to neighbor cells. The proposed handoff algorithm allows fast and seamless intersector handoffs. In addition, two unique techniques are used for enhanced handoff performance and interference reduction. Disjoint links and fast handoff ensure best link performance and minimum interference to other sectors. Beacon signaling is a novel way of transmitting small control messages in an OFDM system. The proposed handoff techniques make use of beacon signaling to transmit pilots in other carrier frequencies, allowing for fast and seamless handoff in a multicarrier deployment and/or an asynchronous deployment, enabling early discovery of neighbor sectors, thereby minimizing handoff delay.