Performance Comparison of Dynamic Guard Channel Assignment with Buffered Prioritized Scheme for Mobile WiMAX Network

Abstract—Priority is usually given to handover traffic in mobile communication but doing so has the tendency of increasing call blocking probability. It was said previously that non-prioritized call traffic channel assignment scheme reduces call blocking probability more than other basic channel assignment schemes at high handover traffic intensities. A comparison of channel assignment schemes by analysis and MATLAB simulation in this research has shown that dynamic guard channel assignment scheme based on channel utilization minimizes call blocking probability better than non-prioritized, prioritized guard channel and prioritized guard channel with queue/buffer. The wireless technology used was Mobile WiMAX with mobile assisted handover (MAHO) and the queueing policy employed was M/M/C/Q with FCFS service discipline

Improving Prioritized Handover Performance for Mobile WiMAX by Dynamic Guard Channel Allocation and RSS Quality Factor

In cellular communication, guard channel has been used to provide priority to ongoing call traffic crossing cell boundaries in handover process but the major concern is that most guard channel allocation scheme are fixed channels. System congestion problems arising from traffic pattern in the real world is another major concern relating to fixed allocation of guard channels let alone the huge traffic that will emanate from user mobility in the envisaged converged traffic of 4G networks. Hence, dynamic guard channel (DGC) allocation based on traffic intensity or channel utilization of each traffic type was used in this research and it reduced the new call blocking probability better than the fixed prioritized guard channel (PGC) and non-prioritized channel allocation scheme. Its performance in terms of call dropping probability reduction is comparable with the PGC and slightly better off at poor signal condition. It was revealed that DGC averaged QoS better than the existing channel assignment schemes. An investigation into the RSS quality factor (QF) proposed also, showed that at high quality RSS the blocking and dropping probability of the traffic were reduced for the Mobile WiMAX wireless technology network with mobile assisted handover

Geophysical and hydro-physicochemical evaluation of hand-dug wells near a dumpsite in Oyo state, Nigeria

Access to potable water has become a difficult task in many countries of the world including Nigeria. In Nigeria, the government is trying her best to make water supply available to the masses but till now this vision has never been accomplished. If those living in urban areas could not have access to water supply by government, what is the fate of the people living in rural areas? Therefore, exploitation of groundwater through the construction of hand-dug wells is a major source of drinking water for majority of the populace as many could not afford the high cost of drilling borehole. Many people construct these hand-dug wells without linings because they believe that groundwater is the safest water for consumption without considering the environment these wells will be sited and other factors regarding to its construction. The aim of this present study is to evaluate the groundwater resources at Aarada waste disposal site, Ogbomoso, Oyo State, Nigeria. An electromagnetic survey to locate leachate plumes migration pathways was conducted around Aarada refuse dumpsite, Ogbomosho, Oyo State, Nigeria using the VLFEM method. A total of seven VLF-EM profiles were carried out with length ranging between 60 to 150m. Hydrophysicochemical analysis was also conducted at the peak of the raining season on six water samples taken from six different hand-dug wells in the research area. The result obtained from the processed VLF-EM data revealed the presence of leachate (contaminant fluid) at the subsurface in the area. The water quality analysis report showed hazardously high values of Fe2+, Pb2+, Zn2+, Cu2+ and NO3 - to confirm the findings from the VLF-EM surve

Groundwater Contaminats’ Investigation at Aarada Waste Disposal Site Using Geophysical and Hydro-Physicochemical Approach.

A research on the impact of waste disposal site on groundwater resources was conducted around Aarada area, Ogbomosho, Oyo State, Nigeria using electrical resistivity (vertical electrical sounding) and hydro-physicochemical methods. This study was carried out to map the contamination patches at the subsurface and investigate the contamination level of the various hand dug wells situated in the area. A total of seven VES were carried out with length ranging between 80 to 130m. The hydro-physicochemical analysis was conducted at the peak of the wet season on nine water samples taken from nine different hand-dug wells in the research area. The result obtained from the interpreted VES data revealed leachate plumes at the subsurface in the study area. The outcome of the hydro-physicochemical method revealed hazardously high values of Fe2+, Pb2+, Zn2+, Cu2+ and NO3 - to further support the findings from the VES surve

Interpretation of groundmagnetic data in Oke-Ogba Area, Akure, Southwestern Nigeria

Groundmagnetic method was used to delineate into the subsurface in Oke-Ogba area, Akure, which falls within latitude 070 14′ to 070 19′ North and longitude 0050 06′ to 0050 12′ East Southwestern Nigeria, with a view to determining the competent areas for engineering purposes and the promising areas for hydrogeologic prospects. A total of four traverses were established for the purpose of the groundmagnetic study, and the results were presented as groundmagnetic profiles of varying magnetic intensities. The result of investigation revealed that the intensities and characteristics nature of the magnetic anomalies as expressed by all profiles are indicative of the different rock types producing them. Qualitative and quantitative interpretation of individual magnetic anomaly and geological knowledge of the survey area yielded information on the depth of geological features (e.g. rock contact, faults or fractures), structures and magnetic properties of rock units. From the preliminary interpretation, the existence of some structural features such as a likely fault, fracture and contacts between rocks as well as relatively mineralized zones that might contain magnetic minerals of essential magnetite origin is revealed. It was also revealed that Oke- Ogba area, Akure, Southwestern Nigeria is averagely competent for both engineering purposes and hydrogeologic purposes

Assessment of radon concentration in groundwater within Ogbomoso, SW Nigeria

The study is aimed at investigating the level of radon and to determine the health effect connected to radon in drinking water. A total of thirty (30) water samples were randomly investigated in Ogbomoso using an active electronic device RAD 7, produced by Durridge Company USA. The radon concentrations within the study area vary from 0.60 to 2.64 Bq L-1 , with the mean value of 1.86 Bq L-1 . The committed annual effective doses due to ingestion vary from 6.25 × 10-3 to 1.93 × 10-2 mSv y-1 , with mean values of 0.02 mSv y-1 . The radon concentrations in water samples of Ogbomoso are lower than the threshold as set by both United States Environmental and Protection Agency, and European Commission of 11 and 100 Bq L-1 respectivel

IMPACT ASSESSMENT OF SOLID WASTE ON GROUNDWATER: A CASE STUDY OF AARADA DUMPSITE, NIGERIA

A research on the impact of waste disposal site on groundwater resources was conducted around Aarada refuse dumpsite, Ogbomosho, Oyo State, Nigeria using electrical resistivity (Vertical Electrical Sounding) and hydrophysicochemical methods. World Health Organization (WHO) standard was used as yard stick for the hydrophysicochemical method. A total of seven VES were carried out with electrode spacing ranging between 80 to 130m. The hydro-physicochemical analysis was conducted at the peak of the dry season on nine water samples taken from nine different hand-dug wells in the research area. The result obtained from the interpreted VES data revealed leachate plumes at the subsurface in the study area. The outcome of the hydro-physicochemical method revealed hazardously high values of Fe2+, Pb2+, Zn2+, Cu2+ and NO3 -

The groundwater potential evaluation at industrial estate Ogbomoso, Southwestern Nigeria

Vertical Electrical Sounding method was used to map Oyo State industrial estate Ogbomoso with a view to determining the groundwater potential of the study area. Ten Vertical Electrical Soundings (VES) were carried out across the area using the schlumberger electrode array configuration with current electrode separation (AB) varying from 130 m to 200 m. Nine out of the ten modeled curves were H-type where the remaining one was KH-type. The geoelectric sections obtained from the sounding curves revealed 3-layer and 4-layer earth models respectively. The models showed the subsurface layers categorized into the topsoil, weathered/clay, fractured layers and the fresh bedrock. The weathered basement and fractured basement are the aquifer types delineated for the area. Groundwater potential evaluated from the maps (i.e. overburden thickness, anisotropic coefficient, weathered layer isothickness, weathered layer isoresistivity, transverse resistance and bedrock relief maps) revealed that the Southern and Eastern parts of the study area are the most promising region for borehole development. However, Northeastern region of the study area can also be considered as fair for borehole development

GROUNDMAGNETIC INVESTIGATION INTO THE CAUSE OF THE SUBSIDENCE IN THE ABANDONED LOCAL GOVERNMENT SECRETARIAT, OGBOMOSO, NIGERIA

Groundmagnetic was used to investigate the cause of the subsidence at an Abandoned Local Government Secretariat, Ogbomoso, Southwestern Nigeria with a view to determining whether the sinking and cracks in the plasterworks experienced at the Eastern side of the study area is due to subsurface features or insufficient use of building materials. The study took place at an Abandoned Local Government Secretariat Ogbomoso, Southwestern Nigeria which falls within latitude 080 09′ 50.6″ - 080 09′ 55.9″ and longitude 0040 15′ 36.1″ - 0040 15′ 42.3″. Proton Precision Magnetometer model GSM-19T was used to carry out the geophysical survey along four traverses in East-West and North- South directions. The traverses length ranges from 70m to 150m with inter station spacing of 10m. The results were presented as groundmagnetic profiles of varying magnetic intensities, groundmagnetic contoured map and groundmagnetic surface map. The basement topography was obtained from the profiles using half-width of the amplitude method. Areas with high magnetic values are the competent zones for construction while areas with low magnetic values are the weak zones. The quantitative interpretation gave the overburden thickness to the top of the magnetic basement rock as varied between 7.0m to 13.0m. Interpretation of groundmagnetic data revealed that the weak zones present at the Southeastern, Eastern and Northeastern part of the study area are the cause for the subsidence that occurred towards the Eastern side of the building. Contrary to the opinion of people that the building contractor used inferior building materials for the construction, we found out that half of the building is constructed on either collapse tunnel, fault or fracture which resulted into the sinking and new cracks in plasterworks experienced at the Eastern part of the abandoned Local Government secretariat