The wireless-access networks of today will have to evolve in several dimensions in order to address the challenges and expectations of the future. New technology components will be introduced as part of the evolution of current wireless-access technologies, such as HSPA and LTE. However, additional components may also constitute future new wireless-access technologies, which may complement the evolved technologies. Examples of such new technology components are new ways of accessing spectrum and substantially higher frequency ranges, the introduction of massive antenna configurations, direct device-to-device communication, and ultra-dense deployments.

In this paper, we present a pilot design for an OFDM cellular system based on Costas arrays. The design provides pilot symbols for both common and dedicated pilots for MIMO transmission. The pilot symbols are designed so that pilots from different cells intersect minimally. The design results in a large number of available distinct pilot symbol patterns with minimally overlapping resource elements that may be assigned to different cells which simplifies cell planning. The design is described in the context of IEEE 802.16m, but is applicable to any OFDM system. Performance of the pilot design in noise and interference limited environments is presented and is shown to be on par with currently used pilot designs while providing a larger number of patterns.

We develop a physical layer abstraction to model the performance of MIMO with maximum likelihood demodulation (MLD) in a system simulation. MLD is inherently a non-linear process, and thus it is difficult to find a linear abstraction to its performance. The abstraction is based on bounds on performance obtained from the QR & QL decompositions of the channel. The accuracy of the abstraction is demonstrated using link simulations. In addition, the abstraction has low complexity. The model is used in a system simulation to evaluate the gains obtained with MLD.

EDGE has enabled the GSM network to offer third generation services as part of the UMTS core network. This is due to the introduction of 8PSK modulation and the recent specification of interfaces from the GERAN to the UMTS core network. This paper studies further improvements to the spectral efficiency and capacity of EDGE through the use of more sophisticated adaptive modulation schemes based on QAM, and the use of novel turbo coding schemes. Furthermore, this work considers a novel transmit diversity scheme adapted for use in dispersive channels. We provide performance results for the enhanced system showing tremendous gains. We also use theoretical predictions of outage analysis to predict the gain in performance obtained by the use of higher order modulations and transmit diversity. The gains from theoretical predictions match our simulations almost exactly.

The GSM/EDGE Radio Access Network (GERAN) is presently being evolved as a full complement to the 3G UMTS network. One part of this evolution is the introduction of efficient support of real-time packet data and alignment to the UNITS Core Network. Another part will introduce performance-enhancing features aimed at improving spectral efficiency, peak and average user-throughput and capacity. One such enhancement being considered is the use of Higher Level Modulations to enhance the user peak rate in the GERAN, in much the same way as the data rate for GPRS was enhanced with the 8PSK modulation in EDGE. By introducing new coding schemes based on QAM the maximum bit rate per time slot could be increased up to 88.8 kbit/s. This paper explains the GERAN concept and investigates possible system level gains, from both spectrum efficiency and perceived user quality perspective, with Higher Level Modulation in GERAN.

EDGE has enabled GSM networks to offer third generation services as part of the UMTS core network. This has been possible through two steps: the introduction of 8PSK modulation and the specification of interfaces from the GERAN (GSM/EDGE radio access network) to the UMTS core network. This paper studies further improvements to spectral efficiency and capacity for EDGE through the use of more sophisticated adaptive modulation schemes, and the use of newer coding schemes (see Nanda, S. et al., IEEE Commun. Mag., p.54-64, 2000; Ikeda, T. et al., IEEE Trans. Vehic. Tech., vol.49, p.404-12, 2000). It is possible to use theoretical predictions of outage analysis to predict the gain in performance due to the use of higher order modulations.

We consider the problem of calculating the traffic allowable for a certain grade of service in a cellular network employing both AMPS and IS-136 channels. The dual-mode capability of the IS-136 users enables the system to assign them to AMPS channels if IS-136 channels are blocked, hence the two pools of users cannot be treated independently. An analytical method for the calculation of the traffic is derived and the actual capacity improvements obtained by a partial deployment of IS-136 are shown. We also consider the case of reconfigurable transceivers at the base station and derive the traffic allowable. It is seen that a significant increase in traffic is achieved by this option.

Continuous phase modulation (CPM) signals may be precoded by a convolutional code followed by a mapping rule. Better codes may, however, be obtained by a more general code formed by a finite state machine. We provide improved codes for one such finite state machine. A new description of codes and design rules are presented. Better results are demonstrated for the partial response CPM schemes and previous optimum results are matched for the full response case. Tests of an M-algorithm decoder achieve near maximum-likelihood performance with only a fraction of the complexity of the Viterbi algorithm.>

The decision depth function of a convolutional code L/sub D/(w) is the first trellis depth at which all unmerged incorrect subset paths exceed weight w. The authors tabulate this function for most codes in common use. L/sub D/(w) specifies the path memory length of a decoder. It follows a clear asymptotic growth rule.>