Radio Resource Allocation for OSC Downlink Channels

In Voice services over Adaptive Multi-user channels on One Slot (VAMOS), which has been standardized as an extension to the Global System for Mobile Communications (GSM), the concept of Orthogonal Sub-channels (OSC) is employed. Two overlaid Gaussian minimum-shift keying (GMSK) signals are transmitted in the same time slot and on the same frequency. The aim of VAMOS is to approximately double the cell capacity compared to the legacy GSM system. This work studies the downlink radio resource allocation problem. The base station (BS) can decide which users should share the same time and frequency resource within a cell. Additionally, the power allocation for each user must be considered along with a limitation of the subchannel power imbalance ratio (SCPIR) of the users in each pair. Due to frequency hopping (FH) an estimation of the co-channel interference level is not possible. Therefore, this paper proposes a radio resource allocation scheme that allocates resources without the exact knowledge of the actual interference situation. To reduce the energy consumption of the BS, the resources are allocated for a minimum sum transmit power taking into account a prescribed target frame error rate (FER) at the receiver. Simulation results show that with the proposed resource allocation scheme a significant reduction of the required transmit power is possible. Furthermore, the influence of the equalizers on the FER performance, and therefore also the energy savings are evaluated, considering different VAMOS receiver algorithms.