Sung-Geun Jin

Numerical Analysis of the Power Saving in 3GPP LTE Advanced Wireless Networks

We analyze the power-saving operation in Third-Generation Partnership Project (3GPP) Long-Term Evolution Advanced (LTE Advanced) wireless networks. Typically, it is an exhausting and complicated job to numerically analyze the performance of power-saving operations since it is necessary to carefully consider every possible probability, make probability-generating functions, and differentiate these functions. Instead, we develop a totally new approach toward simple but accurate derivations. For this purpose, we divide the time period for the steady-state power-saving operation into several independent parts. Then, we analyze the power-saving operation in each part and thereafter combine the results into an aggregate result. The new approach enables us to avoid sophisticated steps while we reach an accurate analytical model. The equations are validated through comparison with simulation results.

M-PSM: Mobility-Aware Power Save Mode for IEEE 802.11 WLANs

With the proliferation of Wi-Fi equipped mobile devices such as smart phones, it becomes even more important to design and implement effective power management schemes for Wi-Fi interfaces so that the battery lifetime can be prolonged. In this paper, we propose an enhancement to the default 802.11 Power Save Mode (PSM), called M-PSM, which exploits additional power-saving opportunities by considering user mobility and detailed traffic condition when making the sleep/wakeup schedules for Wi-Fi interfaces. We have implemented M-PSM in the Madwifi device driver and demonstrated its effectiveness via experiments and trace-based simulations.

Adaptive sleep mode management in IEEE 802.16m wireless metropolitan area networks

The emerging IEEE 802.16m standard provides a new sleep mode operation for Mobile Stations (MSs). It evolves from the sleep mode operation in the IEEE 802.16 standard but with more advanced features, e.g., the listening window may be extended and the sleep cycle length is adjustable. To fully exploit these advancements, we conduct a comprehensive analytical study on the power consumption and average packet delay under the new sleep mode operation. Then, based on the analytical results, we propose a novel adaptive sleep mode management scheme called Adaptive Sleep Mode Management (ASMM), which adjusts an MSs sleep cycle and listening window in an adaptive manner based on online monitoring and estimation of the traffic condition. The goal is to minimize the power consumption by the MS while limiting the average packet delay under a user-specified level. The effectiveness of ASMM is demonstrated via simulation-based performance evaluation.

Performance analysis of IEEE 802.16m sleep mode for heterogeneous traffic

We numerically analyze the performance of the emerging 802.16 ms sleep mode operation in order to gain a new insight regarding its power consumption and traffic transmission delay when a Mobile Station (MS) in the sleep mode is served with both non-realtime and realtime traffic simultaneously. We validate the analysis via the comparison with simulation results.

Multiple WNIC-based handoff in IEEE 802.11 WLANs

We propose a novel scanning scheme for IEEE 802.11 by equipping Access Points (APs) with multiple Wireless Network Interface Cards (Multi-WNICs), one of which is set to operate in an exclusively reserved channel for the scanning purpose. In this environment, a STAtion (STA) can easily search neighboring APs by scanning the reserved channel. Our simulation results demonstrate that the proposed scheme ultimately reduces the overall scanning time to improve the handoff latency.

Idle mode for deep power save in IEEE 802.11 WLANs

Along with the wide acceptance of IEEE 802.11 wireless local area network (WLAN), new applications such as Internet protocol (IP) telephony over WLAN are fast emerging today. For battery-powered IP phone devices, the life time extension is a key concern for the market acceptance while todays 802.11 is not optimized for such an operation. In this paper, we propose a novel idle mode operation, which comprises paging, idle handoff, and delayed handoff. Under the idle mode operation, a mobile host (MH) without any active session does not need to perform hand-off within a predefined paging area (PA). Only when it enters a new PA, an idle handoff is performed. The proposed idle mode allows an MH without traffic to extend its life time. We develop a new analytical model in order to comparatively evaluate our proposed scheme. The numerical results demonstrate that the proposed scheme outperforms the existing schemes with respect to power consumption.

A MAC/PHY cross-layer design for efficient ARQ protocols

In many wireless data systems, automatic repeat request (ARQ) and hybrid automatic repeat request (HARQ) work independently. In this paper, we introduce a new ARQ feedback scheme called Cross-Layer ARQ (CL-ARQ), where ARQ closely interoperates with HARQ by making use of the acknowledgement of HARQ internally. By doing so, CL-ARQ not only removes the overhead for ARQ acknowledgement messages, but also improves the average delivery delay and TCP throughput. Especially, when the entities in charge of HARQ and ARQ are located far apart geographically, CL-ARQ remarkably outperforms the legacy scheme.

A Novel Idle Mode Operation in IEEE 802.11 WLANs

While the IEEE 802.11 Wireless Local Area Network (WLAN) became a prevailing technology for the broadband wireless Internet access, new applications such as Internet Protocol (IP) telephony are fast emerging today. For the battery-powered IP phone devices, the standby time extension is a key concern for the market acceptance while todays 802.11 is not optimized for such an operation. In this paper, we propose a novel Idle Mode operation, which comprises paging, idle handoff, and delayed handoff. Under the idle mode operation, a Mobile Host (MH) does not need to perform a handoff within a predefined Paging Area (PA). Only when the MH enters a new PA, an idle handoff is performed with a minimum level of signaling. Due to the absence of such idle mode operation, both IP paging and Power Saving Mode (PSM) have been considered the alternatives so far even though they are not efficient. We develop a new analytical model to comparatively evaluate our proposed scheme. Our numerical results demonstrate that the proposed scheme outperforms the legacy alternatives with respect to power consumption, thus extending the standby time dramatically.

Fast scanning schemes for IEEE 802.11 WLANs in virtual AP environments

Abstract Recently, provisioning a fast handoff in IEEE 802.11 Wireless Local Area Network (WLAN) has been an attractive research issue since the incurring latencies are unsatisfactory to support today’s fast emerging realtime services with stringent Quality of Service (QoS) requirements. The 802.11 handoff consists of (1) scanning, (2) authentication, and (3) reassociation. Particularly, the scanning has been studied intensively since it accounts for a major portion of the handoff latency due to potential overheads in the scanning operation. That is, (1) a scanning STAtion (STA) should stay in a scanned channel waiting for Access Points (APs)’ responses without any assurances of APs’ existence after request frame transmissions; moreover, (2) per-channel waiting time is not explicitly defined in the 802.11 standard. In order to reduce the overheads, we propose novel scanning schemes composed of two phases: (1) channel selection phase; and (2) AP search phase. In the channel selection phase, a scanning STA identifies and selects the channels suitable for the 802.11 scanning by assessing all employed channels with Request-to-Send/Clear-to-Send (RTS/CTS) handshaking in a virtual AP environment. Then, in the AP search phase, it performs a unicast-based scanning in order to search for an AP suitable for its handoff in a selected channel. For a proper handoff decision depending on STA’s requirement, we build two algorithms referred to as first-fit and near best-fit algorithms, respectively. We demonstrate the superiority of our proposed schemes to existing approaches via simulations with realistic time-varying channel models in various simulation environments. The simulation results demonstrate that the proposed scanning schemes provide relatively shorter handoff latencies as (1) a scanning STA has shorter channel switching time; (2) an 802.11 WLAN employs more channels; and (3) the APs are deployed more densely.

A novel idle mode operation in IEEE 802.11 WLANs: prototype implementation and empirical evaluation

While the IEEE 802.11 Wireless Local Area Network (WLAN) became a prevailing technology for the broadband wireless Internet access, new applications such as Internet Protocol (IP) telephony are fast emerging today. For the battery-powered IP phone devices, the standby time extension is a key concern for the market acceptance while todays 802.11 is not optimized for such an operation. In this paper, we propose a novel Idle Mode operation, which comprises paging, idle handoff, and delayed handoff. Under the idle mode operation, a Mobile Host (MH) does not need to perform a handoff within a predefined Paging Area (PA). Only when the MH enters a new PA, an idle handoff is performed with a minimum level of signaling. Due to the absence of such idle mode operation, both IP paging and Power Saving Mode (PSM) have been considered the alternatives so far even though they are not efficient. We develop a new analytical model to comparatively evaluate our proposed scheme. Our numerical results demonstrate that the proposed scheme outperforms the legacy alternatives with respect to power consumption, thus extending the standby time dramatically.