Phone Lin

Channel allocation for GPRS

Based on the GSM radio architecture, the general packet radio service (GPRS) provides users data connections with variable data rates and high bandwidth efficiency. In the GPRS service, allocation of physical channels is flexible, i.e., multiple channels can be allocated to a user. We propose four algorithms for the GPRS radio resource allocation: fixed resource allocation (FRA), dynamic resource allocation (DRA), fixed resource allocation with queue capability (FRAQ), and dynamic resource allocation with queue capability (DRAQ). We develop analytic and simulation models to evaluate the performance for these resource allocation algorithms in terms of the acceptance rate of both GPRS packet data and GSM voice calls. Our study indicates that DRAQ (queuing for both new and handoff calls) outperforms other algorithms.

OVSF code channel assignment for IMT-2000

Code channel assignment deals with the problem that how different codes are allocated to different connections. In the 3GPP technical specifications, the channelization codes used for spreading are orthogonal variable spreading factor (OVSF) codes. It can preserve the orthogonality between users physical channels. OVSF codes are valuable resources in CDMA systems and should be properly managed. The objective of this paper is to find a code channel assignment method to support as many users as possible with less complexity. We proposed a code channel assignment method for user equipment (UE) that has the capability to support multi-rate services using multi-code transmission. A single table is used to allocate codes to a UE according to its requested data rate. Therefore, the allocation and releasing procedures, which can be accomplished in a very short period of time, are efficient.

A Region-Based Clustering Mechanism for Channel Access in Vehicular Ad Hoc Networks

Several contention-based Medium Access Control (MAC) protocols have been proposed for the vehicles to gain the radio channels to distribute active safety messages timely, e.g., Safety Critical Application (SCA) information, for inter-vehicle communications in Vehicular Ad Hoc Networks (VANETs). In these MAC protocols, a contention period is introduced before the vehicle for channel access so that we may not have the timely and reliably message dissemination in VANETs. To reduce the contention period, this paper proposes a Region-based Clustering Mechanism (RCM) to be applied in these MAC protocols. We propose analytical models to investigate the performance of the RCM, which are validated by the simulation experiments.

A study on distributed/centralized scheduling for wireless mesh network

The IEEE 802.16 standard proposes the Media Access Control (MAC) protocol for the Wireless Metropolitan Area Network (WMAN). Two transmission modes are defined in the IEEE 802.16, including Point-to-Multipoint (PMP) mode and mesh mode. In the 802.16 mesh mode, allocation of minislots can be handled by the centralized and distributed scheduling mechanisms. This paper proposes the Combined Distributed and Centralized (CDC) scheme to combine the distributed scheduling and centralized scheduling mechanisms so that the minislot allocation can be more flexible, and the utilization is increased. Two scheduling algorithms, Round Robin (RR) and Greedy, are proposed as the baseline algorithms for the centralized scheduling mechanism. We conduct simulation experiments to investigate the performance of the CDC scheme with the RR and Greedy algorithms. Our study indicates that with CDC scheme, the minislot utilization can be significantly increased.

Optimal Placement of Gateways in Vehicular Networks

In vehicular networks, mobile users in vehicles can access the Internet and enjoy various kinds of services such as Voice over IP (VoIP) and online streaming video. To provide satisfactory quality of service (QoS), we need to appropriately place gateways to link mobile nodes to the Internet or any other information networks. In this paper, we address the problem of optimally placing gateways in vehicular networks to minimize the average number of hops from access points (APs) to gateways, so that the communication delay can be minimized. Moreover, we also investigate how to minimize the total power consumption, and we show that, when the average number of hops is minimized, the average capacity of each AP can be maximized.

Mobility Management Strategy Based on User Mobility Patterns in Wireless Networks

Mobility management plays an important role in wireless communication networks in effectively delivering services to users on the move. Many schemes have been proposed and investigated extensively in the past to improve performance. Profile-based scheme (PBS) is one of them, which uses the user routine information stored in the user profile to reduce location update signaling traffic. To improve PBS performance, in this paper, a new location management scheme called the mobility-pattern-based scheme (MPBS) is proposed, which incorporates the time information in the user profile so that a users current location can be determined by his/her movement state and the current system time. Extensive simulations have been carried out, and the results show that the MPBS scheme can mitigate the signaling traffic load significantly while reducing paging delay at the same time

Design and Performance Study for a Mobility Management Mechanism (WMM) Using Location Cache for Wireless Mesh Networks

Wireless mesh networks (WMNs) have emerged as one of the major technologies for 4G high-speed mobile networks. In a WMN, a mesh backhaul connects the WMN with the Internet, and mesh access points (MAPs) provide wireless network access service to mobile stations (MSs). The MAPs are stationary and connected through the wireless mesh links. Due to MS mobility in WMNs, mobility management (MM) is required to efficiently and correctly route the packets to MSs. We propose an MM mechanism named Wireless mesh Mobility Management (WMM). The WMM adopts the location cache approach, where mesh backhaul and MAPs (referred to as mesh nodes (MNs)) cache the MSs location information while routing the data for the MS. The MM is exercised when MNs route the packets. We implement the WMM and conduct an analytical model and simulation experiments to investigate the performance of WMM. We compare the signaling and routing cost between WMM and other existing MM protocols. Our study shows that WMM has light signaling overhead and low implementation cost.

Channel allocation for GPRS with buffering mechanisms

General Packet Radio Service (GPRS) provides mobile users end-to-end packet-switched services by sharing the radio channels with voice and circuit-switched services. In such a system, radio resource allocation for circuit-switched and packet-switched services is an important issue, which may affect the QoS for both services significantly. In this paper, we propose two algorithms: Dynamic Resource Allocation with Voice and Packet queues (DRAVP) and Dynamic Resource Allocation with Packet and Voice queues (DRAPV) for channel allocation of the voice calls and packets. We propose analytic and simulation models to investigate the performance of DRAVP and DRAPV in terms of voice call incompletion probability, packet dropping probability, average voice call waiting time, and average packet waiting time. Our study indicates that the buffering mechanism for GPRS packets significantly increase the acceptance rate of GPRS packets at the cost of slightly degrading the performance of voice calls.

Group Mobility Management for Large-Scale Machine-to-Machine Mobile Networking

Machine-to-machine (M2M) communications have emerged as a new communication paradigm to support Internet of Things (IoT) applications. Millions to trillions of machines will connect to mobile communication networks (MCNs) to provide IoT applications. This group-based behavior is considered one of the features of M2M communications. That is, machines are likely with correlated mobility and may perform mobility management at the same time. As a result of this scenario, signaling exchanges for machines are more likely to occur at the same time, and the random access channel (RACH) for the signaling is more likely to be congested. In this paper, we propose a group mobility management (GMM) mechanism where machines are grouped based on the similarity of their mobility patterns at the location database (LDB), and only the leader machine performs mobility management on behalf of the other machines in the same group. The GMM mechanism attempts to mitigate the signaling congestion problem. Through our performance study, we show how the GMM mechanism can reduce registration signaling from machines.

Reducing Signaling Overhead for Femtocell/Macrocell Networks

Femtocell technology has been proposed to offload user data traffic from the macrocell to the femtocell and extend the limited coverage of the macrocell in mobile communications networks. In existing commercial femtocell/macrocell networks, a widely accepted solution to configure the location areas (LAs) is to partition the femtocells overlapped with a macrocell into small groups and to assign each group with a unique LA ID different from that of the macrocell. Such configuration can reduce the paging cost in the mobility management, but increases registration signaling overhead due to discontinuous coverage of femtocells. To reduce signaling overhead in the femtocell/macrocell network, we propose a delay registration (DR) algorithm that postpones the registration until the delay timer expires when the mobile station (MS) moves into the overlapped femtocell. Analytical models and simulation experiments are proposed to investigate the performance of the DR algorithm. Our analytical models are generally enough to accommodate various MS mobility behaviors. Our study can provide guidelines for the operators to set up a delay timer to reduce signaling overhead while sustaining the traffic offloading capability of the femtocell.