System-Level Analysis of Closed-Loop Power Control in the Uplink of DS-CDMA Cellular Networks

A system-level model for power control in the uplink of direct-sequence code-division multiple access (DS-CDMA) cellular networks is presented. The model takes into account the effects of the closed loop, namely average transmit power rise, power headroom, and variable soft hand-off gains, which are not considered in existing power control models. The power control problem is analyzed in this setting, and a number of properties are derived which generalize results from the classical model without closed-loop effects. Based on this analysis, an algorithm is given that determines required transmit powers taking into account these effects. This algorithm is a generalization of classical iterative algorithms without closed-loop effects. Finally, simulation results are presented to assess the validity of the approach

Variable step closed-loop power control with space diversity for low elevation angle High Altitude Platforms communication channel [Langkah variabel kontrol daya tertutup dengan keragaman ruang untuk sudut elevasi rendah pada kanal komunikasi HAPs]

This paper proposes variable step closed loop power control algorithm combined with space diversity to improve the performance of High Altitude Platforms (HAPs) communication at low elevation angle using Code Division Multiple Access (CDMA). In this contribution, we first develop HAPs channel model which is derived from experimental measurement. From our experiment, we found HAPs channel characteristic can be modeled as a Ricean distribution because the presence of line of sight path. Different elevation angle resulting different K factor value.  This value is then used in Signal to Interference Ratio (SIR) based closed loop power control evaluation. The variable step algorithm is simulated under various elevation angles with different speed of mobile user. The performance is presented in terms of user elevation angle, user speed, step size and space diversity order. We found that the performance of variable step closed-loop power control less effective at low elevation angle. However our simulation shows that space diversity is able to improve the performance of closed loop power control for HAPs channel at low elevation angle.*****Kajian ini mengusulkan suatu algoritma kontrol daya langkah variabel loop tertutup dikombinasikan dengan keragaman ruang untuk meningkatkan kinerja komunikasi High Altitude Platforms(HAPs) pada sudut elevasi rendah menggunakan Code Division Multiple Access (CDMA). Kami berkontribusi untuk mengembangkan model kanal HAPs yang berasal dari pengukuran eksperimental sebelumnya. Dari percobaan tersebut, kami menemukan karakteristik kanal HAPs yang dapat dimodelkan sebagai distribusi Ricean karena kehadiran jalur tanpa penghalang. Eksperimen menunjukkan bahwa perbedaan sudut elevasi menghasilkan perbedaan nilai factor K. Nilai ini kemudian digunakan dalam Signal to Interference Ratio (SIR) berbasiskan evaluasi kontrol daya loop tertutup. Algoritma langkah variabel disimulasikan dibawah sudut elevasi yang berbeda dengan kecepatan yang berbeda dari pengguna vobile. Kinerja tersebut disajikan dalam hal sudut elevasi pengguna, kecepatan pengguna, ukuran langkah dan ketertiban ruang keanekaragaman. Kami menemukan bahwa kinerja langkah variabel kontrol daya loop tertutup kurang efektif pada sudut elevasi rendah. Namun simulasi kami menunjukkan bahwa ruang keragaman mampu meningkatkan kinerja kontrol daya loop tertutup untuk kanal HAPs di sudut elevasi rendah.

Soft handover issues in radio resource management for 3G WCDMA networks

PhDMobile terminals allow users to access services while on the move. This unique feature has driven the rapid growth in the mobile network industry, changing it from a new technology into a massive industry within less than two decades. Handover is the essential functionality for dealing with the mobility of the mobile users. Compared with the conventional hard handover employed in the GSM mobile networks, the soft handover used in IS-95 and being proposed for 3G has better performance on both link and system level. Previous work on soft handover has led to several algorithms being proposed and extensive research has been conducted on the performance analysis and parameters optimisation of these algorithms. Most of the previous analysis focused on the uplink direction. However, in future mobile networks, the downlink is more likely to be the bottleneck of the system capacity because of the asymmetric nature of new services, such as Internet traffic. In this thesis, an in-depth study of the soft handover effects on the downlink direction of WCDMA networks is carried out, leading to a new method of optimising soft handover for maximising the downlink capacity and a new power control approach

Variable Step Closed Loop Power Control with Space Diversity for Low Elevation Angle High Altitude Platforms Communication Channel [Langkah Variabel Kontrol Daya Loop Tertutup Dengan Keragaman Ruang Untuk Sudut Elevasi Rendah Pada Kanal Komunikasi HAPs]

This paper proposes variable step closed loop power control algorithm combined with space diversity to improve the performance of High Altitude Platforms (HAPs) communication at low elevation angle using Code Division Multiple Access (CDMA). In this contribution, we first develop HAPs channel model which is derived from experimental measurement. From our experiment, we found HAPs channel characteristic can be modeled as a Ricean distribution because the presence of line of sight path. Different elevation angle resulting different K factor value. This value is then used in Signal to Interference Ratio (SIR) based closed loop power control evaluation. The variable step algorithm is simulated under various elevation angles with different speed of mobile user. The performance is presented in terms of user elevation angle, user speed, step size and space diversity order. We found that the performance of variable step closed-loop power control less effective at low elevation angle. However our simulation shows that space diversity is able to improve the performance of closed loop power control for HAPs channel at low elevation angle.*****Kajian ini mengusulkan suatu algoritma kontrol daya langkah variabel loop tertutup dikombinasikan dengan keragaman ruang untuk meningkatkan kinerja komunikasi High Altitude Platforms(HAPs) pada sudut elevasi rendah menggunakan Code Division Multiple Access (CDMA). Kami berkontribusi untuk mengembangkan model kanal HAPs yang berasal dari pengukuran eksperimental sebelumnya. Dari percobaan tersebut, kami menemukan karakteristik kanal HAPs yang dapat dimodelkan sebagai distribusi Ricean karena kehadiran jalur tanpa penghalang. Eksperimen menunjukkan bahwa perbedaan sudut elevasi menghasilkan perbedaan nilai factor K. Nilai ini kemudian digunakan dalam Signal to Interference Ratio (SIR) berbasiskan evaluasi kontrol daya loop tertutup. Algoritma langkah variabel disimulasikan dibawah sudut elevasi yang berbeda dengan kecepatan yang berbeda dari pengguna vobile. Kinerja tersebut disajikan dalam hal sudut elevasi pengguna, kecepatan pengguna, ukuran langkah dan ketertiban ruang keanekaragaman. Kami menemukan bahwa kinerja langkah variabel kontrol daya loop tertutup kurang efektif pada sudut elevasi rendah. Namun simulasi kami menunjukkan bahwa ruang keragaman mampu meningkatkan kinerja kontrol daya loop tertutup untuk kanal HAPs di sudut elevasi rendah

A Game-theoretic Approach To Uplink Power Control In Cdma Networks

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2011Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2011Kablosuz iletişim ağlarında temel kaynaklar olan bant genişliği (spektrum) ve güç sınırlıdır. Bu nedenle, bu kaynakların verimli kullanımı önem kazanmıştır. Bu yüzden DS-CDMA türü çoklu erişimin kullanıldığı sistemlerde telsiz kaynaklarının yönetiminde güç kontrolü önemli bir gerekliliktir. DS-CDMA sistemi girişim kısıtlı olduğundan dolayı, herhangi bir kullanıcı bencilce hareket ederek, kullanıcıdan erişim noktasına olan kendi iletim gücünü arttırarak, kendi servis kalitesini arttırılabilir. Ancak bu artış diğer kullanıcılara için istenmeyen girişime sebebiyet verir. Servis kalitesi, sinyal girişim oranına (SIR) bağlıdır ve yüksek SIR elde etmek için yüksek iletim gücüne ihtiyaç vardır, bununla beraber bit hata oranı (BER) düşmekte ve böylece daha yüksek bir veri aktarımı elde edilmektedir. Ayrıca, kullanıcının iletim gücünü arttırması, pil tüketimini hızlandırmakta bu da kullanıcının memnuniyetini azaltmaktadır. Bu sebeple, SIR ve iletim gücü değerlerinin mobil kullanıcılar için önem kazanmaya başlar ve kullanıcılar bir yandan yüksek SIR elde etmek isterken aynı zamanda düşük enerji tüketmek ister. Bu iki çelişen amaç arasında iyi bir denge kurmak, DS-CDMA ağlarında telsiz kaynaklarının yönetiminin bir parçası olan güç kontrolünün ana odak noktasıdır. Güç kontrolü çoğunlukla ortak kanal girişimini azaltmak ve SIR değerini garanti altına alarak daha iyi bir servis kalitesi elde etmek amacıyla kullanılır. Bu tez çalışmasında, kablosuz haberleşme şebekelerinde güç kontrolü için en genel yaklaşımlardan biri olan güç dengeleme veya diğer adıyla SIR dengeleme yaklaşımı incelenmiştir. Güç dengeleme algoritmaları basit ve çoğu dağıtık olarak gerçekleştirilmektedir ancak yakınsama açısından oldukça yavaş olması dezavantajdır. Son yıllarda, oyun teorisi alternatif bir yaklaşım olarak veri şebekelerinde güç kontrolü çalışmaları için kullanılmıştır. Bu tez çalışmasında, DS-CDMA sistemlerin yukarı yönde iletişimindeki güç kontrolü probleminin oyun teorisi yaklaşımıyla ele alınması incelenmiştir. Bu problem çok kullanıcılı ve kullanıcılar arasında herhangi bir işbirliğinin olmadığı ve her kullanıcının kendi kazancını maksimize etmeye çalıştığı N-oyunculu işbirliksiz bir oyun olarak modellenmiştir. Her kullanıcı için tanımlanan kazanç fonksiyonu, SIR ve iletim gücüne bağlı olarak kullanıcının tercihini gösterir. Her bir kullanıcı için enerji verimliliğine ve yüksek hizmet kalitesine teşvik edici kazanç fonksiyonları tanımlanmıştır. Kazanç fonksiyonuna bağlı olarak, belirtilen oyunda optimum çalışma noktası olarak ifade edilen bir adet “Nash dengesinin” var olduğu gösterilmiştir. Bunun yanında, yukarı yöndeki güç kontrolü için güç dengeleme algoritması ve oyun kuramı yaklaşımı uygulanmış ve güce karşılık gelen iterasyon sayısı baz alınarak analiz edilmiştir. Benzetim sonuçları karşılaştırılmış ve oyun kuramı yaklaşımının, güç dengeleme algoritmasından daha iyi sonuçlar verdiği gösterilmiştir.In wireless communication networks, fundamental resources that are bandwidth (spectrum) and power are limited. For this reason, efficient use of these resources becomes important. Therefore, power control is an essential requirement for radio resource management in the design of wireless systems, especially in direct-sequence code-division multiple-access (DS-CDMA) systems. Since DS-CDMA system is interference-limited, when a user acts selfishly to improve its quality-of-service (QoS) requirements by increasing its individual transmit power at the uplink that causes unnecessary interference to other users in the cell. QoS depends on the signal-to-interference ratio (SIR) and achieving a high SIR requires a high transmit power, though, resulting in a lower bit-error rate (BER) and thus higher throughput. Additionally, increasing the transmit power of a user expedites its battery drain, which reduces the satisfaction of the mobile user. Hence, SIR and transmit power become valuable commodities, thus a wireless user prefers to obtain high SIR and to consume low energy. Finding a good balance between two conflicting objectives is the main focus of the power control component of radio resource management in CDMA networks. Power control has mainly used to reduce co-channel interference and to guarantee SIR, resulting better QoS. In this thesis, one of the most common approaches to power control in wireless communication networks which is power balancing, also called SIR balancing is considered. Power balancing algorithms are simple and most of them can be implemented distributively, but have the disadvantage that convergence can be slow and it is guaranteed only if every mobile’s target SIR is feasible. In recent years, an alternative approach based on game theory has been used to study power control in data networks. In this thesis, the application of game theory for studying uplink power control in DS-CDMA network is considered. Power control problem is modeled as a N-person non-cooperative game in which each mobile user tries to maximize its own utility without any deal among the users. A utility function is defined for each user, which represents the user’s choice with respect to the SIR and the transmitter power. For a proper utility function, it is shown that there exists an optimum operating point referred to as a “Nash equilibrium” that is unique. Furthermore, power balancing algorithm and game theoretic approach to uplink power control were implemented and analyzed based on power versus number of iterations. A comparison of simulation results are carried out. The game theoretic power control algorithm was shown to give better results compared to SIR balancing power control algorithm.Yüksek LisansM.Sc

A novel mobile communication system using Pulse Position based Chirp Spread Spectrum modulation

The paper presents a new mobile communication system based on Chirp Spread Spectrum (CSS) transmission. The downlink modulation scheme is extended with Pulse Position Modulation (PPM) to carry data for multiple mobile terminals simultaneously. The described novel mechanism ensures reliable and robust communication between the parties, especially for terminals moving with high speeds or at long range. Furthermore, the proposed system take care of the uplink communication as well, where Closed-Loop Power Control (CLPC) is applied to handle the near-far problem and improve the performance of the system. Based on the attributes of the proposed system the application area covers sensor networks, IoT applications and Industry 4.0 as general field of LPWAN, however, mobility of terminals also considered.Analytical investigations for downlink communication are described focusing on the instantaneous symbol-error rate and average SER in Rayleigh fading channel. The results show that the proposed Pulse Position based Chirp Spread Spectrum technique for Multiple Access (shortly PP-CSS-MA) allows higher data rates that is used for the multiple access feature. In addition, numerical results are presented as well, and they point out the benefits of the applied CLPC mechanism. Finally, considerations regarding to the implementation of the proposed communication system are described

An intelligent-agent approach for managing congestion in W-CDMA networks

PhDResource Management is a crucial aspect in the next generation cellular networks since the use of W-CDMA technology gives an inherent flexibility in managing the system capacity. The concept of a “Service Level Agreement” (SLA) also plays a very important role as it is the means to guarantee the quality of service provided to the customers in response to the level of service to which they have subscribed. Hence there is a need to introduce effective SLA-based policies as part of the radio resource management. This work proposes the application of intelligent agents in SLA-based control in resource management, especially when congestion occurs. The work demonstrates the ability of intelligent agents in improving and maintaining the quality of service to meet the required SLA as the congestion occurs. A particularly novel aspect of this work is the use of learning (here Case Based Reasoning) to predict the control strategies to be imposed. As the system environment changes, the most suitable policy will be implemented. When congestion occurs, the system either proposes the solution by recalling from experience (if the event is similar to what has been previously solved) or recalculates the solution from its knowledge (if the event is new). With this approach, the system performance will be monitored at all times and a suitable policy can be immediately applied as the system environment changes, resulting in maintaining the system quality of service