Josefina Castañeda-Camacho

Reverse link erlang capacity of multiclass CDMA cellular system considering nonideal antenna sectorization

In this paper, the effect of antenna sectorization in the reverse link erlang capacity of a multiclass code-division multiple-access (CDMA) cellular system is studied. Traditionally, it has been considered that the capacity is multiplied by a factor equal to the number of sectors introduced. This is true only in the ideal antenna sectored system. However, due to the nonideal antenna radiation pattern, the sectorization gain is smaller than the number of sectors. Our contribution is the analytical study of the effect of nonideal antenna patterns on the capacity of a multiclass CDMA system. We also present an approximated analysis of the erlang capacity, considering that blocking in CDMA occurs when the interference reaches a predetermined level above the background noise level of mainly thermal origin. The analysis also includes the effects of imperfect power control and service activity detection. We found that the capacity losses due to the consideration of antenna sectorization are about 20.20% for the nonideal antenna radiation pattern and 30.32% for the evaluated commercial radiation pattern. This percentage loss implies that the sectorization gain is approximately 2.39 for a nonideal antenna pattern and 2.09 for a commercial antenna pattern in typical conditions, /spl mu/=4 and /spl alpha/=8 dB.

Erlang capacity of multiclass CDMA cellular system

In this paper we evaluate the reverse link capacity of direct sequence-code division multiple access (DS-CDMA) cellular system supporting multiclass services. We present an approximated analysis of the Erlang capacity, considering that blocking in CDMA occurs when the interference level reaches a predetermined level above the background noise level of mainly thermal origin. We investigate the effect of important factors on capacity: (1) variation of the energy-to-interference E/sub b//I/sub 0/ ratio according to propagation conditions for each multiservice user, (2) multiservice user activity, (3) multicode or multirate transmission, (4) handoff, (5) Poisson arrival process and (6) non uniform load in each cell.

Erlang capacity of overlaid multiclass CDMA and TDMA systems

In this paper we evaluate the reverse link Erlang capacity of a multiclass CDMA and TDMA systems when they are overlaid. We consider the Poisson nature of the arrivals in both systems and an interesting variation of the Erlang loss model used in TDMA system with the additional assumption of an ordered hunt. That is, we assume that the TDMA slots are numbered 1,2,...,N/sub TS/ in a way that co-channel slots are placed at the end of the list, thus each arriving user takes the lowest-numbered idle slot. It is shown that the capacity in the overlay situation considering an ordered hunt can be significantly increased. In our analysis we obtain a capacity increase on the IS-136 system due to the CDMA2000 overlay of a factor equal to 0.58-2.8 for an outage ranging from 10.61% to 19.08% in the IS-136 system and a blocking probability, P/sub b/=2%, in the CDMA2000 system.

Overlay of TDMA and multiclass CDMA systems with slots reallocation on the TDMA layer

This paper extends and complements a previous research where we show that the overlay of multicast CDMA and TDMA systems is possible with the assumption of an ordered hunt. In this work, we present a new scheme of overlay situation in which the cochannel TDMA slots are placed at the end of the list but with the additional assumption of a slots reallocation (reallocation control model), in order to reduce the TDMA interference to CDMA layer and increase the overlay capacity. It means that if one slot is set free among the first m ordered busy slots, the user who occupies the m-th slot (last position) will be reallocated to the released position. Comparing with the pure ordered hunt scheme we have obtained an important improvement on the capacity due to the reallocation strategy, associated to a better performance on the TDMA system in terms of the outage probability.

Forward link capacity of overlaid multiclass CDMA systems and TDMA systems with slots reallocation on the TDMA layer

In this paper we evaluate the forward link Erlang capacity of a multiclass CDMA and TDMA systems when they are overlaid. Additionally, we propose two schemes for the overlay situation, ordered hunt and slots reallocation (reallocation control model). For the ordered hunt scheme we assume that the TDMA slots are numbered 1,2,...,N/sub TS/ in a way that co-channel slots are placed at the end of the list, and each arriving user takes the lowest-numbered idle slot, in order to reduce the TDMA interference to CDMA layer and increase the overlay capacity. In the second scheme, the co-channel slots are placed at the end of the list but with the additional assumption of slots reallocation. It means that if one slot is set free among the first m ordered busy slots, the user who occupies the m-th slot (last position) will be reallocated to the released position. The objective to the slots reallocation is to achieve the occupancy of the co-channel slots as low it is possible. In our results we obtain that the overlay situation in the forward link is possible under the proposed strategies.

CDMA 1xEVDO System with Smart Antenna Array

Smart antennas have received increasing interest due to its capability for improving the performance of wireless radio systems. In this work we studied the throughput maximization in a CDMA 1xEV-DO cellular system when a smart antenna array is implemented. We focus in the downlink of the CDMA cellular system and consider a packet data direct-sequence code division multiple access (DS-CDMA). We show that it is possible to obtain a significant increment in the throughput of the system due to the switched beam smart antenna array.

On the use of notch filters and ordered co-channel TDMA slots strategies to the TDMA and CDMA overlaid systems

CDMA and TDMA overlay has been investigated as a way to take advantage of the bandwidth available in narrowband systems. It has been demonstrated that without notch filters and ordered co-channel TDMA slots strategies, CDMA and TDMA coexistence cannot be achieved in practical situations. The use of notch filtering rejects only part of the intracell interference generated from the TDMA system but the ordered co-channel TDMA slots strategies decrease the intercell interference which could not be rejected by the filters. We have considered that the two systems share the same frequency bandwidth and power control on both layers. The performance of the overlaid system has been analyzed in the CDMA and TDMA layers in terms of blocking probability and outage probability.

On the restriction of the coverage area of the interference TDMA co-channel slots in an overlaid CDMA and TDMA system

Theoretically the separation of CDMA and narrowband waveforms can be done through notch filters; however it has been demonstrated that the filtering techniques are not enough to eliminate the multi-cross interference problem. As a means of suppressing the interference that can not be eliminated by the use of filters this work presents a new proposal in which the reduction of the coverage area of the interference TDMA co-channel slots and the ordering in the use of this slots can significantly reduce the effect of the TDMA interference over the CDMA system. Thus, a TDMA sector is divided in two concentric zones, each one associated with a different set of slots. We divide the set of slots in two groups a general group C/sub G/ integrated by all non-co-channel slots and a restricted group C/sub R/ integrated by the co-channel slots. In the inner region the two groups of slots can be used but in the outer zone only the C/sub G/ group is used. Thus, with this strategy the effect of the co-channel interference is minimized. The performance evaluation of the overlaid system is derived analytically in terms of the Erlang capacity of the two systems for different scenarios, different concentric regions areas and for the reverse and forward links.

Overlay of a wireless local loop system on CDMA2000 cellular system

The overlay of a wireless local loop system on the CDMA2000 cellular system is proposed. The CDMA2000 system uses 5, 10, 15 and 20 MHz of dispersion bandwidth and the WLL system uses 1.25 MHz of dispersion bandwidth. In this way, it is possible to have 3, 4, 8, 9, 12 and 16 frequency allocations for the WLL system depending on the different bandwidths of the CDMA2000 cellular system. As an overlay system the WLL can use only a fraction of the frequency allocations according to co-frequency allocation reuse distance, similar to FDMA and TDMA cellular systems. With this idea less interference is introduced in the WLL system (in the limit, the capacity will be similar to the isolated cell) keeping at the same value the interference introduced in the CDMA cellular system.

Overlay of CDMA2000 on IS-136

The forward and reverse link capacities of CDMA2000 and IS-136 are evaluated when they are overlaid. It is assumed that IS-136 support mainly voice services and that CDMA2000 support different services with different rates and quality requirements. Multicode and variable processing gain are studied. Moreover, as CDMA2000 can use 1.25 MHz and 5 MHz of dispersion bandwidth in the 25 MHz cellular bandwidth it is possible to have 20 and 5 frequency allocations with different reuse patterns as in FDMA and TDMA cellular systems. This idea allows us to have very high capacity in the CDMA system with the installation of less equipment in comparison with the universal frequency reuse.