Optimal cluster-based routing scheme using node mobility in ad hoc networks

Ad hoc networks have a scalability problem. When the nodes of an ad hoc network increase in number or mobility, the amount of control traffic for routing increases and could cause traffic congestion. Cluster-based routing schemes have been proposed as a solution to this problem. Typical cluster-based ad hoc networks use a proactive routing scheme for intra-cluster routes and a reactive routing scheme for inter-cluster routes. In this study, we propose a new cluster-based routing scheme for ad hoc networks which makes use of the mobility of nodes. Nodes are divided into two groups on the basis of their mobility. For a route search within a cluster, a proactive routing scheme is used for low-mobility nodes and a flooding-based reactive routing scheme is used for high-mobility nodes. The required control traffic of the proposed scheme is analyzed and optimal parameters of the proposed scheme are derived from the analysis. The numerical results show that the proposed scheme produces far less control traffic than a typical cluster-based routing scheme.     

A batch‐update strategy for the distributed HLRs architecture in PCS networks

Owing to the increasing population of mobile subscribers, the rapidly expanding signaling traffic has become a challenge to the mobility management in PCS networks. Multiple database schemes to reduce signal traffic and to solve the bottleneck problem of the single home location register (HLR) architecture have been proposed by many researchers. However, in most of the multiple location databases or HLR systems, extra signaling is required for the multiple database updates. We propose a batch‐update strategy, instead of the immediate update method, for the location‐tracking schemes with replication to reduce the signaling overhead. In this paper, we first introduce a distributed HLRs architecture in which each HLR is associated with a localized set of VLRs and the location registrations and queries are processed locally. Then we propose our batch‐update strategy and present two pointing schemes for inter‐HLR call deliveries. The numerical result shows that our approach can effectively decrease the signaling cost of location registration and call delivery compared with the IS‐41 standard. Copyright © 2002 John Wiley & Sons, Ltd.     

Performance analysis of cache strategy for signaling traffic management in a wireless ATM network

In a wireless ATM network for mobile multimedia services, conventional signaling protocols generate heavy traffic because the signaling load must be handled in a HLR (Home Location Register). This centralized structure of the wireless ATM network causes critical connection setup delays. Thus, distributed processing based on a reduction of the connection setup delays is needed in wireless ATM networks. A cache strategy for call delivery with cache updates of registration based on ATM multicasting is introduced with a comparison of the cost of cache scheme with the cost of a conventional scheme. Results show that the cache scheme has better performance than conventional methods when portable mobility is low with large traffic density. This revised version was published online in July 2006 with corrections to the Cover Date.     

Location management in mobile ad hoc wireless networks using quorums and clusters

Position‐based reactive routing is a scalable solution for routing in mobile ad hoc networks. The route discovery algorithm in position‐based routing can be efficiently implemented only if the source knows the current address of the destination. In this paper, a quorum‐based location management scheme is proposed. Location servers are selected using the minimum dominating set (MDS) approach, and are further organized into quorums for location update and location query. When a mobile node moves, it updates its location servers in the update quorum; when a node requests the location information of another node, it will send a query message to the location servers in the query quorum. We propose to use the position‐based quorum system, which is easy to construct and guarantees that the update quorums always intersect with the query quorums so that at least one location server in the query quorum is aware of the most recent location of the mobile node. Clusters are introduced for large scale ad hoc networks for scalability. Experiment results show that the proposed scheme provides good scalability when network size increases. Copyright © 2005 John Wiley & Sons, Ltd.     

带门槛的环形搜索移动性管理策略中移动台所 越过的位置区环数

位置管理或移动性管理是移动计算研究领域的一个具有挑战性的问题.我国及其他国家目前正在使用的个人通信网络如GSM、IS-41中,用两层数据库HLR/VLR支持位置管理.在这些网络中,每当移动台从一个位置区LA(Location area)移动到另一个位置区,其基本的位置管理策略(简称"基本策略")不管是否必要均立即进行位置更新操作,因而造成系统资源的极大浪费,降低了系统的性能.本文给出一种带门槛的环形搜索策略(简称"门槛环形策略")——将位置区分成环,设定一个门槛(整数),当移动台越过的位置区的环数没有达到门槛时,系统不进行位置更新操作,以减少位置管理的费用.在假定移动台的呼入是一个泊松过程,移动台在各个位置区的逗留时间是符合一般概率分布的随机变量的条件下,推导出在两次呼入之间移动台处于各位置区环的概率及移动台所越过的位置区环数公式,给出了"门槛环形策略"的位置管理费用小于"基本策略"的条件.     

Two-level pointer forwarding strategy for location management in PCS networks

For a IPCS network to effectively deliver services to its mobile users, it must have an efficient way to keep track of the mobile users. The location management fulfills this task through location registration and paging. To reduce the signaling traffic, many schemes such as a local anchor (LA) scheme, per-user caching scheme and pointer forwarding scheme have been proposed in the past. In this paper, we present a new location management scheme which intends to mitigate the signaling traffic as well as reduce the tracking delay in the PCS systems. In this strategy, we choose a set of visitor location registers (VLRs) traversed by users as the mobility agents (MA), which form another level of management in order to make some registration signaling traffic localized. The idea is as follows: instead of always updating to the home location register (HLR), which would become the bottleneck otherwise, many location updates are carried out in the mobility agents. Thus, the two-level pointer forwarding scheme is designed to reduce the signaling traffic: pointers can be set up between VLRs as the traditional pointer forwarding scheme and can also be set up between MAs. The numerical results show that this strategy can significantly reduce the network signaling traffic for users with low CMR without increasing much of the call setup delay.     

Improving mobile ad hoc network routing with satellite out‐of‐band signaling

Routing in mobile ad hoc networks is a complex task due to the mobility of the nodes and the constraints linked to a wireless multihop network (e.g., limited bandwidth, collisions, and bit errors). These adverse conditions impair not only data traffic but also routing signaling traffic, which feeds route computation. In this contribution, we propose to use satellite communications to help in the distribution of mobile ad hoc network routing signaling. The optimized link‐state routing (OLSR) is chosen among several routing protocols to be extended with satellite‐based signaling, yielding a version we call OLSR hybrid signaling (OLSR‐H). This new scheme is evaluated through simulations and yields improvements of approximately 10% in the data delivery ratio compared with a regular OLSR. This evaluation is conducted using two different network topology models, one being fit for representing forest firefighting operations. Copyright © 2013 John Wiley & Sons, Ltd.     

On the effect of group mobility to data replication in ad hoc networks

The growth in wireless communication technologies attracts a considerable amount of attention in mobile ad hoc networks. Since mobile hosts in an ad hoc network usually move freely, the topology of the network changes dynamically and disconnection occurs frequently. These characteristics make it likely for a mobile ad hoc network to be separated into several disconnected partitions, and the data accessibility is hence reduced. Several schemes are proposed to alleviate the reduction of data accessibility by replicating data items. However, little research effort was elaborated upon exploiting the group mobility where the group mobility refers to the phenomenon that several mobile nodes tend to move together. In this paper, we address the problem of replica allocation in a mobile ad hoc network by exploring group mobility. We first analyze the group mobility model and derive several theoretical results. In light of these results, we propose a replica allocation scheme to improve the data accessibility. Several experiments are conducted to evaluate the performance of the proposed scheme. The experimental results show that the proposed scheme is able to not only obtain higher data accessibility, but also produce lower network traffic than prior schemes.     

Location tracking with distributed HLR's and pointer forwarding

Location tracking operations in a personal communications service (PCS) network are expensive. A location tracking algorithm called pointer forwarding has been proposed to reduce the location update cost. The key observation behind forwarding is that if users change PCS registration areas (RAs) frequently, but receive calls relatively infrequently, it should be possible to avoid registrations at the home-location register (HLR) database by simply setting up a forwarding pointer from the previous visitor-location register (VLR). Calls to a given user will first query the user's HLR to determine the first VLR, which the user was registered at, and then follow a chain of forwarding pointers to the user's current VLR. To reduce the “find” cost in call delivery, the PCS provider may distribute HLR databases in the network. This paper integrates the concept of distributed HLRs with pointer forwarding, and the new scheme is referred to as the pointer forwarding with distributed HLR (PFDHLR). Since no registration to the HLR is performed in the pointer forwarding scheme when a user moves to the new locations, the cost of updating multiple HLRs is eliminated in PFDHLR. Our study indicates that PFDHLR may significantly reduce the mobility management cost compared with the single HLR approach     

Channel Allocation Scheme for Handoff Control in Wireless Ad Hoc Network with Group Mobility

Because a wireless ad hoc network does not have a fixed backbone network and the mobile base station moves randomly, the conventional channel allocation scheme cannot efficiently predict group mobility and is not feasible to support a burst handoff traffic due to group mobility. In this paper, we propose an channel allocation scheme to solve this problem. Our scheme efficiently support burst handoff using guard channel and hello message in wireless ad hoc network with group mobility. We developed an analytical Markov model for the proposed scheme and evaluate our scheme in terms of new call and handoff blocking probability and channel utilization via simulation study. Simulation results show that our scheme offers better performance than the conventional schemes.     

Local anchor scheme for reducing signaling costs in personalcommunications networks

A personal communications network (PCN) location tracking scheme called local anchoring is introduced which reduces the signalling cost as compared to the location management strategy proposed in the IS-41 standard. Local anchoring reduces the number of location registration messages between the home location register (HLR) and the visitor location registers (VLRs) in a way that location change is reported to a nearby VLR called the local anchor (LA) instead of to the HLR. This method successfully reduces the cost for location tracking when the call arrival rate is low relative to the mobility rate and the cost for location registration is high. A dynamic local anchoring mechanism is then introduced which dynamically selects the LA such that the expected cost for location registration and call delivery can be further reduced. It is demonstrated that the cost of dynamic local anchoring is always lower than or equal to that of the IS-41 scheme     

Mitigating location management traffic via aggregation in multi-hop cellular networks

In high mobility areas such as shopping malls and transportation stations, mobile users tend to move in and out in a bursty fashion, and hence location update (LU) and paging signaling cause substantial traffic burden to the cellular networks, leading to signaling congestion. This poses a great challenge to the system design for wireless cellular systems. Traditional cellular systems cannot cope with this situation very well. However, with the ad hoc operational mode recently introduced into the cellular systems, the added multi-hop relaying via mobile devices provides a new way to mitigate location management traffic. In this paper, based on this new architecture, we propose a novel scheme, called aggregative location management, which aggregates multiple location updates into group location updates. For the scenarios of high capacity transit (HCT) systems, we use this grouping scheme to alleviate the signaling traffic when mobile users in an HCT move into new location areas. For other scenarios with mass arrivals of LU requests, we develop a generic aggregative location management scheme in which LU requests can be first aggregated by designated mobile devices and then are periodically sent to the location registers. Performance evaluation is carried out and shows their significant effectiveness.     

Comparing the PCS location tracking strategies

The cache scheme has been proposed to reduce the location tracking overhead of a personal communications services (PCS) network. In the previous papers, we studied the cache scheme under the assumptions that the home location register (HLR) access time is constant and the portable residence times have an exponential distribution. This paper compares the cache scheme with a basic scheme (such as IS-41). We generalize the previous models by considering the queueing effect of the HLR (i.e., we model the HLR by an M/G/1 queue) and by considering an arbitrary distribution for the portable residence times. Our study shows that the cache scheme is likely to outperform the basic scheme when (1) the net traffic to the HLR in the basic scheme saturates and the hit ratio in the cache scheme is larger than zero, (2) the portable mobility is low with respect to the call arrival rate, and (3) the variance of the HLR service time distribution is large (for a fixed mean service time). We also indicate an intuitive result that the cache hit ratio is high for a high call arrival rate and low portable mobility. For a fixed mean portable residence time, we show that a higher cache hit ratio is expected for a portable residence distribution with larger variance     

A Novel Efficient Traffic Estimation Strategy Using Hello Messaging Through Local Link Connectivity in MANETs

Wireless Personal Communications - Network traffic estimation under random mobility of network nodes is one of the key challenges for effective communication in mobile ad hoc networks (MANETs)....     

Dynamic hierarchical database architecture for location managementin PCS networks

This paper introduces a dynamic hierarchical database architecture for location management in personal communications service (PCS) networks. The proposed scheme allows the dynamic adjustments of user location information distribution based on the mobility and calling patterns of the mobile terminals (MTs). A unique distribution strategy is determined for each MT, and location pointers are set up at selected remote locations which indicate the current location of the MTs. This method effectively reduces the signaling and database access overhead for location registration and call delivery. Besides, the required processing is handled by a distributed network of directory registers and centralized coordination is not necessary. The functions of the other network elements, such as the home location register (HLR) and the visitor location registers (VLRs), remain primarily unchanged. This greatly facilitates the deployment of this scheme in current PCS networks     

A Novel Mobility Management Scheme for Integration of Vehicular Ad Hoc Networks and Fixed IP Networks

Integration of vehicular ad hoc network and fixed IP network is important to provide Internet connection and mobile data service for vehicles. However, the unique characteristics of vehicular networks, such as linear topology and constrained movements of vehicles, are not considered in the conventional mobility management schemes. Using conventional schemes, unnecessary management messages are generated and the connections to roadside-installed base stations are not fully utilized. As the results, bandwidth is wasted and data delivery ratio is not maximized. In this paper, we propose a novel mobility management scheme to integrate vehicular ad hoc network and fixed IP networks more efficiently. The proposed scheme manages mobility of vehicles based on street layout as well as the distance between vehicles and base stations. Utilizing the unique characteristics of vehicular networks, the proposed scheme has substantially less mobility management overhead and higher data delivery ratio. The proposed scheme is simulated by SUMO (a vehicular traffic simulator) and QualNet (a data network simulator). The simulation results show that the proposed scheme reduced the mobility management overhead up to 63% and improved the data delivery ratio up to 90%.     

Cooperative Location Management for a Cellular Network with Ad Hoc Communication

The cellular network with ad hoc communication has been foreseen in the next-generation mobile communication system. For such a network, a distance-based (DB) location management scheme cooperated with the ad hoc assistance node (DBCAN) is proposed in this paper. Allowing a mobile terminal to pass its mobility information to the ad hoc assistance node (AAN) with appropriate location updating, DBCAN can effectively reduce the paging cost and limit the paging delay. Moreover, DBCAN includes a method to determine whether AANs should be utilized or not to make cost effective. Our simulation results show that DBCAN can effectively reach cost reduction and still get performance improvement even if the probability to successfully deliver mobility information to AANs falls to the median level.     

基于社会上下文认知的机会路由算法

无线智能设备的普遍使用促进了机会网络的发展.这类网络处于间歇性连接状态,以自组织方式转发数据.路由协议设计时考虑节点携带者的社会特征和日常行为能够提高机会网络的性能.提出了一种基于社会上下文认知的机会路由算法SCOR,该算法利用网络中的社会上下文信息,通过BP神经网络模型预测节点的移动行为.路由决策过程充分考虑移动节点活动的时间和空间属性,当接收节点与发送节点同时处于网络中的同一连通域时,数据转发采用同步方式,否则采用异步方式.仿真分析和实验结果表明,与其它经典算法相比,SCOR算法提高了数据成功转发的比率,减少了网络的开销.     

An adaptive location management scheme for mobile broadband cellular systems

This paper presents an adaptive location management strategy that considers both location updating and paging by evaluating realistic mobility patterns. It proposes the design of an adaptive macro-location area based on multi-registration adapted to the terminals’ trajectory to reduce location updates. The solution includes an estimation of residence probabilities in the areas of the multi-registered list. This facilitates the design of a sequential paging scheme that reduces the average paging cost. Results show the capability of the solution to adapt to mobility patterns and traffic conditions in the network to minimize the overall location cost. Furthermore, the multi-registration approach and the reduced complexity in both network infrastructure and mobile terminals make the solution suitable for new packet-based broadband cellular systems.     

OLSR performance measurement in a military mobile ad hoc network

Wireless ad hoc networks are autonomous, self-configurating and adaptive. Thus, such networks are excellent candidates for military tactical networks, where their ability to be operational rapidly and without any centralized entity is essential. As radio coverage is usually limited, multihop routing is often needed; this is achieved by an ad hoc routing protocol supporting nodes mobility. In this paper, we present performance measurements of the Optimized Link State Routing (OLSR) routing protocol, having the status of IETF RFC. The measurements are performed at CELAR site on a platform representative of military scenarios in urban areas. This platform consists of ten routers, eight PDAs and laptops using a IEEE 802.11b radio interface and implementing OLSR v7. Some nodes are mobile within vehicles. The emphasis of the measurements is on the performance of the network (route repair, network convergence speed, user traffic performance) in presence of this mobility.