Kyunghun Jung

A performance model for admission control in IEEE 802.16

For systems based on connection-oriented services, such as IEEE 802.16, call admission control (CAC) strategy is essential to provide a desired level of quality of service (QoS). Although many handoff-prioritized CAC schemes, which assume a fixed channel capacity, have been introduced, this assumption is not always valid for IEEE 802.16 that uses adaptive modulation and coding (AMC). With AMC, the modulation type of a user’s connection can be changed dynamically and the ongoing connection might fail due to the change of modulation. In this paper, we approach the AMC-induced CAC problem by focusing on the guaranteed connection. Three kinds of calls, new, handoff, and modulation-changed calls, are considered. We propose a modified guard channel CAC scheme that allows the modulation-changed and handoff calls to use the guard channel. Then we analyze a Markov model for the CAC scheme with long-term AMC in mind. According to the simulation results, the proposed approach reduces the call dropping probability for modulation-changed calls, which suggests the threshold of guard channels in IEEE 802.16 can be determined based on the proposed approach.

Comparison of symmetric and asymmetric routing for fixed two-hop cellular relaying network

In this paper, routing strategies for fixed two-hop cellular relaying networks are discussed in terms of area spectral efficiency. We consider symmetric and asymmetric routing in uplink and downlink. Simulation results show that relaying increases the average throughput in comparison with conventional cellular networks and the area spectral efficiency of asymmetric routing is slightly better than that of the symmetric

Markov Model for Admission Control in the Wireless AMC Networks

In wireless adaptive modulation and coding (AMC) systems, modulation type of a users connection can change and the ongoing connection might fail due to the change of modulation. In this paper, we approach the AMC-induced call admission control (CAC) problem by focusing on the guaranteed connection. Three classes of calls, new, handoff, and modulation-changed, are considered. We modify the guard-channel CAC scheme such that the modulation-changed calls, in addition to the handoff calls, are allowed to use the guard channel. Then we analyze a Markov model for the CAC scheme designed with long-term AMC in mind. The proposed approach will be an essential tool to determine the guard-channel thresholds in the wireless AMC networks.

Improving LTE/LTE-A UE Power Efficiency with Extended DRX Cycle

Recently introduced UE types, such as Machine Type Communications (MTC) devices, require extremely efficient power saving mechanisms to operate in harsh situations for a long period with limited charging opportunities. Typical MTC devices, e.g., meters or sensors, access the network very infrequently, once per a few days or even months, but they have to suppress their power consumption as much as possible to survive the period with batteries or internal power sources with limited generation capabilities. During the idle mode in which the activity of UE is minimal, UE has to periodically monitor a control channel, PDCCH, to receive paging messages or identify whether system information is updated. In the LTE/LTE-A nomenclature, such a period is called Discontinuous Reception (DRX) cycle. In this paper, we outline the envisioned gain in power consumption when longer DRX cycle is applied, and explain the procedures to enable longer DRX. We analyze the impact of introducing the feature on the operation of the networks, and provide a guideline to facilitate longer DRX.

Transition from circuit-switched to packet-switched 3G mobile multimedia telephony

3G mobile multimedia telephony is equipped with various measures designed to reduce the audiovisual impact from compression, transmission, and reconstruction process of multimedia over 3G mobile communications networks. In this paper, we summarize the challenges 3G circuit and packet-switched multimedia telephony systems should overcome and explain their key differences in the handling of limited radio resources and hostile channel impairments.

Media and Radio Signal Processing for Mobile Communications

Get to grips with the principles and practice of signal processing used in mobile communications systems. Focusing particularly on speech, video, and modem signal processing, pioneering experts employ a detailed, top-down analytical approach to outline the network architectures and protocol structures of multiple generations of mobile communications systems, identify the logical ranges where media and radio signal processing occur, and analyze the procedures for capturing, compressing, transmitting, and presenting media. Chapters are uniquely structured to show the evolution of network architectures and technical elements between generations up to and including 5G, with an emphasis on maximizing service quality and network capacity through re-using existing infrastructure and technologies. Implementation examples and data taken from commercial networks provide an in-depth insight into the operation of real mobile communications systems, including GSM, cdma2000, W-CDMA, LTE, and LTE-A, making this a practical, hands-on guide for both practicing engineers and graduate students in wireless communications.

Session negotiation and media adaptation of EVS in Voice over LTE

EVS is expected to fill the large gap between the quality and capacity currently available and those expected for 4G, and beyond, mobile communications systems. The large bit-rate and bandwidth ranges, and the complex structures of the new codec make it challenging to deploy and operate. In this paper, we explain how EVS is systematically integrated into the VoLTE ecosystems, outlining session negotiation procedures in which QoS is agreed between two UEs via IMS, and media adaptation procedures in which a controlled compromise is achieved between voice quality and error resilience when the link quality deteriorates or the radio resource runs out.

An overload-resilient flow removal algorithm for M-LWDF scheduler

In the real-time multimedia applications, packet delay should meet stringent Quality of Service (QoS) requirements Delay Earliest Due Date (EDD) scheduler, originally designed for wireline data networks to operate under a maximum allowed delay, cannot be directly applied to wireless networks, due to the location-dependent errors and time-varying channel conditions Several modifications of EDD scheduler have been proposed for wireless applications, which typically assume successful admission control, a condition hard to satisfy with wireless networks In this paper, we propose a removal algorithm for downlink scheduler designed to perform under overloaded situations Simulation results show that our proposed algorithm outperforms the conventional ones in the QoS guaranteed flows.