Benny Vejlgaard

Capacity of a GSM network with fractional loading and random frequency hopping

The need for more capacity in GSM networks is increasing. Using random frequency hopping and fractional loading is a potential way to obtain more capacity. In this paper the optimal reuse scheme for a GSM system with random frequency hopping is presented along with some methods to increase the capacity and to improve the link quality, like using DTX and fractional loading. The 1/3 reuse scheme appears to be best if the capacity is determined by looking at the distribution of signal to interference (CIR) values, while the 3/9 reuse scheme seems best if the focus is at the percentage of dropped calls (with the used dropped call, power control and handover algorithm). The 1/3 reuse scheme has the advantage over the 3/9 reuse scheme that it is able to profit from fractional loading, which gives better quality to the individual user.

Narrowband LTE-M System for M2M Communication

The Internet of Things will bring billions of devices that are inter-connected using cellular networks. LTE cellular systems are being deployed worldwide and will remain in place for the foreseeable future. However, LTE was designed for high data-rate broadband services. Even with M2M features being added in LTE Rel-12, it is not optimized for low data-rate and wide area M2M services such as smart meters, remote sensors, and consumer devices. In this paper, we present a design of a new narrowband M2M system built from existing LTE functionalities for Low Power Wide Area (LPWA) systems. Salient features of this new system include low-cost devices, high coverage, long device battery life, and high capacity. It can be deployed using minimum of one GSM channel and can also share spectrum with existing broadband LTE systems. Cost analysis shows significant reduction compared to LTE UEs. In addition, coverage analysis and capacity results are presented. Finally, coexistence with GSM is analyzed.

Evaluation of Empirical Ray-Tracing Model for an Urban Outdoor Scenario at 73 GHz E-Band

In the summer of 2013, a wideband propagation measurement campaign using rotating directional antennas at 73 GHz was conducted at the New York University (NYU) campus, in order to collect extensive field measurements for use in a millimeter wave (mmWave) E-band statistical channel model. While the measurement campaign provided over 50 Gigabytes of wideband power delay profiles and angular responses [1], [2], the time and labor intensive measurements were based on only 5 transmitter (Tx) locations and 27 receiver (Rx) locations, making up a total of 74 Tx-Rx link combinations. To help generalize the measurements for immediate model development and eventual site planning, this paper presents an empirical ray-tracing model, with the goal of finding a suitable approach such that ray-tracing (RT) can fill in the gaps of the measurements. Here, we use the measured data to investigate the prediction capability of an empirical RT model, in which the 3D model of New York City (including the building structures and interaction losses) are greatly simplified. The comparison between the measured and predicted results show good accuracy is obtained when a simplified RT model is used, suggesting that fast and simple ray tracers will be able to correctly predict the propagation characteristics at mmWave bands.

Performance analysis for UMTS downlink receiver with practical aspects

The theoretical BER is calculated for downlink in UMTS including interpath interference and multiple access interference. The analog interface to the digital receiver is analyzed and an architecture including AGC and ADC is suggested. It is further analyzed that an ADC with 4-5 bit and sampling of 4 times the chip rate will give an acceptable performance within 0.2 dB from the theoretical performance.

Realistic Indoor Wi-Fi and Femto Deployment Study as the Offloading Solution to LTE Macro Networks

This paper investigates the downlink performance of indoor deployed Wi-Fi and Femto as the offloading solution to the LTE macro cellular networks in a realistic large-scale dense-urban scenario. With an assumed broadband traffic volume growth of 50x compared to todays levels, it is evaluated that a dual-carrier LTE macro network will not be able to provide sufficient service coverage with a 1 Mbps minimum data rate and, indoor coverage is identified as the major bottleneck.. We evaluate the performance of indoor Wi-Fi and Femto cell deployment to offload the congested LTE macro network. We show that, in a dual-carrier LTE macro case with a total of 30 MHz spectrum, Wi-Fi access point density of 230/km2 is required to meet the set target of 90% coverage with a minimum user data rate of 1 Mbps. For the same scenario it was found that an out-band Femto access point density of 1200/km2 is required. Furthermore, we show that in-band Femto cell cannot meet the set network requirement even at a very high access point density. We also show that Wi-Fi and Femto cell can offload the same amount of traffic when they are deployed at the same access point density.

Multi-Layer Mobility Load Balancing in a Heterogeneous LTE Network

This paper analyzes the behavior of a distributed Mobility Load Balancing (MLB) scheme in a multi-layer 3GPP (3rd Generation Partnership Project) Long Term Evolution (LTE) deployment with different User Equipment (UE) densities in certain network areas covered with pico cells. Target of the study is to evaluate MLB in terms of efficient pico cell utilization and macro layer load balancing (LB). The analysis focuses on video streaming traffic due to specific service characteristics (e.g. play-out buffer delay/jitter protection) that might make any mobility performance degradation transparent to the end user performance. Results have shown that the proposed MLB scheme can significantly improve the overall network resources utilization by eliminating potential load imbalances amongst the deployment layers and consequently enhance user experience. However this occurs at the cost of increased Radio Link Failures (RLF), a fact that might be critical for further applying MLB in real-time conversational services without additional mobility optimization and interference management techniques.

Interference Measurements in the European 868 MHz ISM Band with Focus on LoRa and SigFox

In this measurement study the signal activity and power levels are measured in the European Industrial, Scientific, and Medical band 863-870 MHz in the city of Aalborg, Denmark. The target is to determine if there is any interference, which may impact deployment of Internet of Things devices. The focus is on the Low Power Wide Area technologies LoRa and SigFox. The measurements show that there is a 22-33 % probability of interfering signals above -105 dBm within the mandatory LoRa and SigFox 868.0-868.6 MHz band in a shopping area and a business park in downtown Aalborg, which thus limits the potential coverage and capacity of LoRa and SigFox. However, the probability of interference is less than 3 % in the three other measurement locations in Aalborg. Finally, a hospital and an industrial area are shown to experience high activity in the RFID subband 865-868 MHz, while the wireless audio band 863-865 MHz has less activity.

Grouped RAKE finger management principle for wideband CDMA

A RAKE finger allocation algorithm for direct-sequence spread-spectrum systems is presented and analyzed. The RAKE finger allocation method is based on grouped RAKE finger assignment. The detected code phases with greatest power are assigned a group of RAKE fingers with equal spacing around the detected code phase. Allocating the RAKE fingers with spacing less than one chip period can reduce overhead for delay tracking. The grouped RAKE finger allocation principle is compared to single RAKE finger allocation. Allocating three RAKE fingers with T/sub c//2 spacing gives a 0.2-0.4 dB gain compared to single RAKE finger assignment with the same number of RAKE and tracking fingers.

Modeling of Wi-Fi IEEE 802.11ac Offloading Performance for 1000x Capacity Expansion of LTE-Advanced

This paper studies indoor Wi-Fi IEEE 802.11ac deployment as a capacity expansion solution of LTE-A (Long Term Evolution-Advanced) network to achieve 1000 times higher capacity. Besides increasing the traffic volume by a factor of x1000, we also increase the minimum target user data rate to 10Mbit/s. The objective is to understand the performance and offloading capability of Wi-Fi 802.11ac at 5GHz. For the performance evaluation of Wi-Fi, we propose a novel analytical throughput model that captures both key 802.11ac enhancements and multi-cell interference. We provide a quantitative evaluation of large-scale indoor Wi-Fi 802.11ac deployment in a real urban scenario by extensive simulations. We conclude that deploying indoor Wi-Fi access points in almost every building is essential to carry the x1000 traffic volume and ensure a minimum user data rate of 10Mbit/s.

Heterogeneous LTE-Advanced Network Expansion for 1000x Capacity

This paper studies LTE (Long-Term Evolution)-Advanced heterogeneous network expansion in a dense urban environment for a 1000 times capacity increase and a 10 times increase of the minimum user data rate requirements. The radio network capacity enhancement via outdoor and indoor small cell densification and utilization of the higher frequency bands has been investigated. As the baseline, we assume a full LTE-Advanced network deployment. Rather than looking at peak data rate, we focus on the end-user experience defined as 90% coverage at a minimum user data rate. We conclude that the 1000 times network capacity increase together with the 10 times increase of minimum user data rate can be reached by LTE-Advanced deployment with approximately 10 times more outdoor micro sites and 100 times more indoor femto cells with respect to the number of macro sites. In terms of spectrum requirements, we have increased the total amount of downlink spectrum to a total of 300 MHz by re-farming spectrum and adding new spectrum in 3.5 GHz band. We conclude that new spectrum at 3.5 GHz is essential to reach the set target network capacity.