During the life time of a call, if the channel conditions become poor, then a higher rate (of loWer SF ) code is assigned to meet the delay requseements of a real-time call.
As an example, we can consider a multi-cell network where the transmitters are base stations (BSs) equipped with multiple antennas that communicate with the single antenna mobile stations (MSs) using time-division-multiple-access.
This type of diversity, in which switching is based on the SIR value, can be measured in real time both in base stations (uplink) and in mobile stations (downlink) using specific SIR estimators.
The specific process is that the AoD information is firstly estimated at mobile stations by using the estimated algorithm (such as multiple signal classification (MUSIC), estimation of signal parameters via rotational invariance techniques (ESPRIT), and subspace algorithms [10, 39]) and then fed back to BS via feedback of downlink channel.
Similarly, TruckPad, another Naspers investment, began as a small venture that displaced physical advert boards at petrol stations using a mobile app.
The articles in [1 6] used nonstatistical methods to locate the mobile station (MS) using network based measurements.
So far, the study reviewed in the previous section concentrated on transmit diversity techniques for SU-MIMO transmission, where each mobile station (MS) uses its transmit antennas to improve the performance at a given throughput, making use of the available spatial diversity.
Since the NodeB or the mobile station can use any of the 512 or 256 OVSF codes, respectively (each parent OVSF of length less than 256 or 512 is interfered by its descendant), we would need to use all the OVSF in order to guarantee that the ones that are actually used are being interfered (a priori, it is not easy to know which ones they are).
The system aims to perform remote acquisitions and transmit them to a central station using mobile telephony.
