Kari Niemela

GSM Evolution Importance in Re-Farming 900 MHz Band

Re-farming of 900 MHz band into HSPA has been started and is likely to happen later with LTE. Typically operators have less than 10 MHz block of 900 MHz spectrum and therefore co-existence of two systems in that band is causing challenges. One of the major issues is the high GSM voice traffic that will remain in the GSM network. How to cope the same traffic with significantly less bandwidth for GSM? Orthogonal Sub-Channel (OSC) is a new method to increase voice capacity in the GSM system. OSC intends not only increase the GSM voice capacity but enables very efficient usage of hardware and spectrum resources. In this paper a detailed analysis on OSC performance is made based on system level simulations. Aim is to provide results that show how OSC can be used for refarming of the 900 MHz band into HSPA or LTE. Simulations are carried in the GSM network evaluating capacity for different bandwidths and site configurations. Released frequency spectrum can be used for HSPA or LTE to provide good coverage for rural area mobile broadband. Results show that OSC is an efficient method to release resources for the new systems.

GSM voice evolution using orthogonal subchannels

The explosive growth of mobile communications, and the overly crowded and expensive spectrum have pushed both system engineers and operators to make their systems as spectrally efficient as possible in order to accommodate the increasing traffic demand. This article is a tutorial introduction to the orthogonal subchannel (OSC) technique. OSC was adopted to improve the capacity of the GSM/EDGE radio access network GERAN, and it is a new concept in which two users can simultaneously share the same GSM radio resource (time slot and frequency) in both the downlink and in uplink directions. Potentially, OSC could not only provide increased network capacity, but also reduce network-associated costs through more efficient usage of hardware and spectrum resources. In addition, this article presents some challenges related to this method, as well as solutions and their respective impact. The results provided herein may contribute to guidelines for network dimensioning and optimization, as well as list potential enhancements to the OSC radio resource management mechanisms needed to further exploit the benefits of OSC. Currently, in real OSC network deployments a capacity gain of 50 percent has been achieved at the cell level. As an indication of the importance of OSC, GSMA awarded it (called Quad Rate) the Best Technology Breakthrough award at Mobile World Congress 2012 [1].

Performance Model for Orthogonal Sub Channel in Noise-Limited Environment

Orthogonal Sub Channel (OSC) is a voice enhancement for the GSM evolution. It allows in principle a double capacity with the same hardware compared to the previous GSM Half Rate (HR) mode. This paper investigates the effects of OSC on the radio performance as function of the OSC capable handset penetration compared to the GSM HR mode. A set of test cases was carried out in GSM network in order to evaluate the radio performance of OSC in terms of the carrier per noise level. The tests were performed in noise-limited indoor environment, and the quality and received power level distributions were analyzed. As a main achievement, a generic model for estimating the effect of OSC on the GSM radio performance was developed. The model is based on the network statistics and performance indicators of GSM.

Capacity Gain Estimation for Orthogonal Sub Channel

OSC (Orthogonal Sub Channel) is an enhancement for the GSM voice traffic. It provides up to double capacity in the GSM radio interface with the same hardware compared to the previous GSM Half Rate (HR) mode. This paper investigates the effects of the OSC on the capacity utilization compared to the GSM HR as function of the OSC capable handset penetration. The variation of the radio network capacity is studied by taking into account the division of the time slot usage between HR and OSC capable terminals. The results show the achievable capacity gains in terms of reduced time slots and transceiver units with given blocking rate.

Variable Bandwidth for GERAN Evolution with Regular Frequency Planning

The further evolution of GSM/EDGE radio access network (GERAN) is currently a subject to standardization in the Third Generation Partnership Project (3GPP). The objectives include significant improvements on user data rates, spectral efficiency and coverage by avoiding concurrent impacts to the existing GSM networks. A variable bandwidth concept, a.k.a. dual symbol rate (DSR) is proposed to meet the demand for uplink enhancements, e.g. settled by camera phones. DSR doubles the modulation rate and user bit rate per radio time slot. It has overlapping transmission bands with regular GSM channel spacing. Numerical results are given to demonstrate possible DSR deployment to the existing networks. Spectral efficiency, coverage and user bit rates are shown to be significantly improved

Dual Symbol Rate for Geran Uplink Evolution

In this paper the dual symbol rate (DSR) concept is proposed for GERAN networks. DSR doubles the modulation rate and user bit rate per radio time slot. Basic assumption is that the transmit signal of adjacent channels overlap in frequency domain. Interference rejection combining algorithms (IRC) are used to combat the introduced interference. Analysis of theoretical channel capacity suggests that data rates can be improved either by increasing the number of antennas or frequency bandwidth in the used radio links. Simulation results are given to demonstrate possible DSR deployment to the existing networks. Spectral efficiency, coverage and user bit rates are shown to be significantly improved

EGPRS2 Uplink Performance for GERAN Evolution

This paper presents a higher performance uplink concept for the evolution of GSM/EDGE radio access network (GERAN). The EGPRS2 UL concept can operate at 1.2 times the current GERAN symbol rate, and employ 4-, 16- and 32-QAM constellations, concatenated with convolutional codes. The interference introduced by the higher transmit signal bandwidth is mitigated by the use of interference rejection combining (IRC) receivers. We explore both noise and interference limited scenarios, in link and system level simulations. The simulation study shows that the user peak data rates can be increased up to 100%, and that the average throughput over practical signal to noise ratio (SNR) conditions can gain up to 50%. Therefore, coverage and user bit rates can be significantly improved without requiring additional radio frequency spectrum.