Multi-antenna aspects of wireless fixed relays

Abstract — Multiple antenna schemes can provide performance enhancement but the small size and cost constraints of wireless terminals preclude their use at these terminals. This paper investigates distributed fixed relays (infrastructure-based relaying) which are engaged in cooperation in a two-hop wireless network as a means of removing the burden of multiple antennas on wireless terminals. In contrast to mobile terminals, a small number of antennas can be deployed on infrastructure-based fixed relays. Hence, the paper investigates performance of the distributed cooperative multi-antenna fixed relays. Threshold maximal ratio combining and threshold selection combining of these multiple antenna signals are studied and analyzed. The following results are derived. For a given performance requirement, the multiple antennas at relays can significantly reduce the number of relays required in a network area, ultimately, reducing system deployment cost. In addition, threshold selection combining at the relays represents an excellent compromise between performance and system cost. Finally, the analysis performed in this paper uses the versatile Nakagami fading channel model. I

Hand book on use and maintenance of small scale agricultural machines

Small-scale farmers are estimated to account for the cultivation of about 90% of the total cultivated land area in Nigeria, producing about 90% of the total agricultural output (CTA, 1997). This category of farmers still depends on manual labour to carry out their various farming operations. However, with labour demand at critical crop production stages, high labour cost and food demand for the teaming population of over 170 million with an annual growth rate of 2.5%, the introduction of agricultural labour saving devices to Nigeria agriculture has become indispensable. Though successive administrations in Nigeria have made concerted efforts aimed at achieving self sufficiency in food production, these efforts have failed to achieve their intended goals. There are many factors responsible for this, a major one being the lack of an integrated and appropriate labour saving agricultural tools and machines. Therefore, the need to develop and introduce more labour saving devices on Nigeria farms has never been more critical than now. Knowing fully well that increased land productivity (greater output per unit of land) generally depends on the application of higher technology and a higher level of knowledge and management ability, it is necessary to appreciate those changes in mechanization level and farm management abilities that can have a multiplier effect on output per unit of land. It is in view of the above that ICRISAT Nigeria is poise with the massive promotion of standardized small and medium scale agricultural machinery and equipment as well as promotes the production of locally designed prototypes in order to help increase the productivity of the poor agrarian community of the country..

Effect of Variety, Soil Moisture Content and Cutting Depth on Performance of a Single Row Animal Drawn Groundnut Digger

The challenge of providing a more efficient and cost-effective ways of harvesting groundnut amongst the small holder farmers is imperative in northern Nigeria as a result of intensity of labor requirement in the task. It is reported that up to 40 % of the total labor required to grow groundnut is expanded on harvesting operation and at peak harvest periods, labor shortages often occur leading to higher costs of production and subsequent years of reduction in yield due to soil nutrient loss owing to the uprooting method of manure harvesting. In order to assuage some of these challenges, a field test was conducted to evaluate operation performance of a single row animal drawn groundnut harvester developed in the department of Agricultural engineering Bayero University Kano. The effects of the control parameters of; variety of the groundnut seed planted, soil moisture content and cutting depth of the digger were studied on the performance parameters of the harvester as; digging efficiency, percentages of exposed pods loss, unexposed pods loss, undug pods loss and total of pods loss. The results obtained revealed a highly significant difference among the varieties with respect to unexposed pod loss (%), while moisture content was found to significantly affect exposed pods loss (%), total pos loss and digging efficiency. Varying the cutting depth significantly affected exposed pods (%), un-exposed pods (%), total pod loss and digging efficiency. Interaction between SAMNUT 23, moisture content of 12.4%db and cutting depth of 15 cm had digging efficiency of 97.22%, while the interactions between SAMNUT 26, moisture content of 12.4%db and cutting depth of 15 cm had digging efficiency of 95.14%. The study revealed that higher digging efficiency is obtainable with higher soil moisture content and cutting depth, irrespective of the variety under cultivation, while correlation analysis revealed that digging efficiency and total percentage of pod loss are inversely related, signifying that at lower digging efficiency there would be higher pod loss and vice versa

Decision feedback equalisation of coded I-Q QPSK in mobile radioenvironments

The bit error rate (BER) performance of equalised I-Q quadrature phase-shift keying (QPSK) is evaluated for wideband cellular systems. Decision feedback equalisation with the square-root Kalman updating algorithm is employed for I-Q coded systems. A gain of about 6 dB is achieved in favour of the I-Q scheme compared with the conventional Gray-mapped QPSK at a BER of 10-

Performance of equalized I-Q 16-QAM in frequency selective fading

The demand for high speed wireless systems dictates the use of bandwidth efficient modulation schemes. Trellis coded I-Q 16-QAM is shown here to be suitable for such applications. The performance of this scheme with decision feedback equalization is evaluated over a two-ray Rayleigh channel. Comparisons between the I-Q scheme with a conventional TCM scheme based on 8-PSK show coding gains of about 4 dB at a BER of 10 -

Performance of equalized I-Q 16-QAM in frequency selective fading

The demand for high speed wireless systems dictates the use of bandwidth efficient modulation schemes. Trellis coded I-Q 16-QAM is shown here to be suitable for such applications. The performance of this scheme with decision feedback equalization is evaluated over a two-ray Rayleigh channel. Comparisons between the I-Q scheme with a conventional TCM scheme based on 8-PSK show coding gains of about 4 dB at a BER of 10 -

Performance of equalized I-Q QPSK over 2-ray Rayleigh fading

In many wideband cellular systems, the channel experiences frequency selective fading. This paper evaluates the bit error rate (BER) performance of equalized I-Q QPSK over frequency selective Rayleigh fading channels. I-Q trellis codes were shown to possess excellent inherent minimum time diversity over flat fading Rayleigh channels. However, they have not been examined for frequency-selective fading channels, where channel equalization is required. In this work, I-Q QPSK systems performance over these channels employing a decision feedback equalizer (DFE) is evaluated. Very reliable communication over the mobile channel is obtained using I-Q QPSK combined with interleaving and adaptive equalization compared to the traditional Gray-mapped trellis code

Performance of equalized I-Q QPSK over 2-ray Rayleigh fading

In many wideband cellular systems, the channel experiences frequency selective fading. This paper evaluates the bit error rate (BER) performance of equalized I-Q QPSK over frequency selective Rayleigh fading channels. I-Q trellis codes were shown to possess excellent inherent minimum time diversity over flat fading Rayleigh channels. However, they have not been examined for frequency-selective fading channels, where channel equalization is required. In this work, I-Q QPSK systems performance over these channels employing a decision feedback equalizer (DFE) is evaluated. Very reliable communication over the mobile channel is obtained using I-Q QPSK combined with interleaving and adaptive equalization compared to the traditional Gray-mapped trellis code