The objective of this study was to investigate the user communities' understanding and interpretation of changes in rangeland use and productivity in the communal lands of Zimbabwe. While external knowledge has been instrumental in defining the drivers and effects of ecological changes hitherto, the role of local knowledge is becoming increasingly important in explaining factors that inform user community perceptions and guide their decisions on the use of rangeland resources. Data on community perceptions were collected in four villages, using Participatory Rural Appraisals in each village and household surveys with a total of 104 households. This study showed that user communities in Nkayi district differentiate rangelands among seven categories of livestock feed resources and how these have changed over time. Communities viewed rangelands not as one continuous, designated and specialized land parcel, but differentiated the land by location, productivity, management and uses in different times of the year. Although land use changes affecting these livestock feed resources were considered to be widespread and multi-directional (both negative and positive) they did not cause widespread degradation. Rangelands converted to croplands were not completely lost, but became important dual purpose land parcels fulfilling both household food security needs and dry season livestock feed requirements. The importance of croplands as a feed resource is reflected in the emergence of new institutions governing their use for livestock grazing and to guarantee security of tenure. On the other hand institutions governing the use of common property rangelands decreased or weakened in their application. The study concludes that while this situation presents ecological challenges for the rangelands, it offers opportunities to find innovative ways of utilizing croplands as the new frontier in the provision of dry season feed resources to smallholder farmers in highly variable environments. Implications for livestock water productivity need to be investigated and water saving technologies should be promoted in the land use intensification processes.

Impulse radio (IR), single-band or multiband, ultra wideband (UWB) systems use simple and low-power-consuming transceivers. Such systems may use low duty cycle time-hopping (TH), leading to low data-rate transmission. Efforts on data rate increase in single-band TH-UWB systems have led to proposal of modulation techniques combining conventional methods and orthogonal pulse shape based schemes. Pulsed multiband systems add abilities for coexistence with narrowband users and frequency-hopping to the IR UWB benefits. This work-inprogress paper proposes use of pulsed multiband approach with combined orthogonal pulse position and bi-orthogonal pulse shape modulation (OPPM-BPSM). A symbol is transmitted at a pseudo-random time-slot on a pseudo-random frequency band using a pseudo-random set of pulse orders in a frame, and the symbol is repeated over a number of frames in a hopping period. A hybrid time-hopping / frequency-hopping / pulse-shapehopping (TH/FH/PSH) multiple-access technique is, thus, proposed. The system can increase data rate through OPPM-BPSM. Analysis shows the system to increase user capacity and to be robust under multiple-access interference in additive white Gaussian noise (AWGN) channels.

A Monte Carlo simulation was conducted to assess the performance of Multi-Carrier Code Division Multiple Access (MC-CDMA) in a sectored cell, in an indoor environment. In each sector, terminals schedule packet transmission using slottedp-persistent Inhibit Sense Multiple Access (ISMA), while the packets themselves are transmitted using MC-CDMA. The simulated bit error rate performance of MC-CDMA with combining strategies maximal ratio combining (MRC) and equal gain combining (EGC) used in the frequency domain are presented. A comparison is made between analytically determined bit error probability for a single user in an additive white Gaussian noise channel using binary phase shift keying (BPSK), and simulated bit error rate for a single user using MC-CDMA with MRC and EGC. The determination of the number of sectors in a cell is also given. MC-CDMA with diversity combining outperforms BPSK in a non-fading AWGN channel. Further, as the user-number increases, EGC performs better than MRC if these combining strategies are used with MC-CDMA. Finally, the results show the basis for determining the number of sectors in a cell. When using slottedp-persistent ISMA, it is envisaged that only a single user will transmit at a time in a sector.