Handover Management of Cellular Communications Systems
CHAPTER ONE
Objective of the study
The overall aim of this study is to enhance the concept and management of cellular communication handover process (es) to support ongoing calls when mobile users are switching between base stations.
In order to achieve the aim of this study, the following objectives are set out as outlined below:
- Analyze call set up failure rate in cellular network operations.
- Investigate cellular handover process failure rate.
- Ascertain call set up time to enhance efficiency and effectiveness of calls made by a mobile station.
- Optimize the Quality of Service (QoS) as a critical performance indicator of the network for efficient service delivery.
CHAPTER TWO
LITERATURE REVIEW
Review of Cellular Network
The cellular network has gone through three generations.
AMPS, the first generation of cellular networks are analog base which majorly grooms the basis for the standard of us cellular network. To increases network capacity, new technologies Time Division Multiple Access (TDMA) and Code Division Multiple Access(CDMA) we used on GSM (Global System for Mobile Communications) second generation to accommodate more mobile terminals. The third generation cellular phone provide such high speed data transmission with voice transmission Perkins (2008).
The Advanced Mobile Phone System (AMPS) is the first commercial cellular system. AMPS were invented by Bell labs and introduced in the early 1980 based on the radio telephone system. AMPS mobile system used analog transmission for voice conservation. AMPS uses FDMA (Frequency Division Multiple Access) which means each consecration is divided by using different channels. Two 25-MHz bands are allocated to amps one for transmission from the base station to mobile terminal (869-894 MHZ), the other for transmission from the mobile terminal to base station (824-849 MHZ). Limitations associated with amps include limited spectrum low calling capacity, poor data communications and minimal privacy.
GSM is a second generation digital cellular system. Digital transmission was used rather than analog transmission in order to improve transmission quality, system capacity, and coverage area. GSM works on three frequencies 900 MHz, 1800 MHz and 1900 MHz. To make efficient use of frequency bands GSM networks uses combination of Frequency Division Multiple Access (FDMA)and Time Division Multiple Access (TDMA).
The general architecture of GSM network is given in fig. below. The GSM system consists of several functional elements including Mobile Switching Centers (MSC), Base Stations (BSC) with associated Base Transceivers (BTS), an Operation and Maintenance Centre (OMC) and gateway MSC.GSM mobile terminal or mobile stations communicates across the Um interface, known as the air interface, with a base BTS in the small cell in which the mobile unit is located. This communication with a BTS takes place through the radio channels. The network coverage area is divided into small regions called cells. Multiple cells are grouped together to form a locations area (LA) for the mobility management Salsano, Polidoro, Mingardi,Niccolini and Veltri (2008).
CHAPTER THREE
MATERIALS AND METHODS
Data Collection and Analysis
In this study, various call quality parameters were evaluated for two GSM mobile operators, i.e operators( a) MTN, operator (b) GLO, with existing infrastructure within Semi-Urban Township Location, Ekpoma. A total of four parameters were evaluated. These parameters are call setup failure rate; handover failure rate; call setup time and performance statistics (QoS indicator).In this study, data collection was obtained from the central monitoring centre called the Operation and Maintenance Centre (OMC), network operation centre (NOC) or the network management centre (NMC) and all inclusive in mobile switching centres.
Data were obtained for the two GSM services operators, MTN and GlO. Reports were initially collected and collated on hourly basis for which average hourly Figures were computed for a day. This progressively translated to an average of seven days taken for a week. The investigation is carried out by considering the causes of handover failure rate, Data were collected from MTN Network (Benin Zone) OMC for a period of one year, from March, 2015 to February, 2016, ten BTS site in Edo State were considered. The additive model was deployed by using relative parameters in the mobile communication network.
CHAPTER FOUR
RESULT AND DISCUSSION
Data Analysis and Results
The data in Table 3.11, which is based on causes of handover drop calls, presented in Figure 4.1. It is observed that four major parameters affect the drop calls handover process in mobile communication network. Based on data obtained for one year, various causes of handover drop calls were highlighted in Figure 4.1. Four basic technical causes were deduced, it was observed that electromagnetic (signal threshold) effects are responsible for highest handover drop calls in the network under investigation. Followed by mobile station end, such as power outage from the mobile station, inefficient credit or air- time and lastly subscribers behaviours can lead to handover drop calls. While the least causes of handover drop calls is natural disaster. Therefore, for effective signal strength at the mobile station the signal strength most be within -50dbm to -120dbm in mobile communication network.
CHAPTER FIVE
CONCLUSION AND RECOMMENDATIONS
Conclusion
The process of handover or handoff within any cellular system is of great importance. It is a critical process and if performed incorrectly handover can result in the loss of the call.
In this research work emphasis has been placed on the differentperformance metrics used to make the handover decision. Also presentations of the most important procedure of GSM handover initiation, handover types and their measurements have been enumerated. Also a great deal of emphasis on mobility in GSM network was given .Very important too is the fact that handover in GSM network is very important to maintain the quality of a call.Handover prioritization schemes were also investigated to prioritize handover calls in order to enhance the quality of service (QoS) of GSM wireless network. Extensive survey and analysis of the handover prioritization schemes that is guard channels, call admission control and handover queuing has been provided. Furthermore the research indicated that different system uses different schemes to execute the handover mechanism for a couple of enhancements to the handover mechanism were introduced and discussed. The idea of the cells overlap and load balancing scheme which tries to equalize the traffic over cells has been introduced. It has been analyzed theoretically and mathematically that capacity depends on the size of the overlapping area between adjacent cells, the number of channels per cells and distribution of traffic. The higher the overlapping area, the higher the trunking efficiency gains. The overlapping area can be used to reduce the call blocking and dropping probabilities. The attractive feature of this scheme is that it organizes traffic in distributed manner and doesn’t increase the system complexity. The implementation of the extensive handover procedures and management as mentioned in this research work will ultimately and significantly impact and improve efficiency and effectiveness in call handover process and overall quality of service,QoS.
This research work contributed the following to telecommunication body of knowledge and the larger society among others:
- Additive model was developed to determine the Handover process performance in mobile network.
- The basic parameters affecting handover process in mobile communication network were highlighted.
- Presentation of an analytical framework to enhance considerably, the handover call mechanism in wireless network and exploration of some of the most viable handover management approaches to serialize and synergize operational efficiency of the signal strength from the base station of the cellular network for capacity utilization and cellular network service delivery.
Recommendations
The following are hereby recommended for greater achievement in further research;
- To research into a much larger area of coverage such as a province or geopolitical region.
- To research into the detection of radio network problems in one or more BTS and finally devise a way to optimize the network and adopt corrective actions like new frequency allocations, antenna tilt adjustment, and parameter modification in the larger database etc.
- To monitor system behaviour and variance in terms of traffic load, congestion, successful attempts etc.
- To predict the upcoming traffic evolution and network expansions as per increasing number of mobile users.
- To benchmark network with another competitor’s network to attract more users at the cost of better quality on a national and global platform.
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