Optimizing Spectrum Use in 3D

Distributed RF Measurement in GSM and CDMA

EE423 Final Report

Group #11

Christian Budiarjo

Kristen Daly

Michelle Teixeira

David Toner

Advisor:

Prof. Tureli

Senior Design Coordinator:

Prof. McNair

Date:

December 6, 2005

Table of Contents

Page #

Abstract 3

Acknowledgement 4

Introduction 5

Design Requirements

Design Objectives 6
System Parameters 6
Design Constraints 7

System Design 8
Financial Budget 9
Project Schedule 10

Task Distribution 11

Conclusion 12

References 13

Gantt Chart 15

Abstract

With the evolution of new technology, a host of intelligent devices will begin to interact with users and communicate with each other. Unfortunately, the resources to support open access to the spectrum do not exist. This accessibility does not exist for two reasons. Firstly, the licensing process for every device will prove to be tedious and expensive. Secondly, it is not feasible to grant access to all mobile devices at every existing location.

These limitations have been an obstacle to wireless application developers. Since these spectrums are already licensed, their availability is limited. However, they are not completely used. Furthermore, since the license holders have complete control over the band, other users cannot use the spectrum. This control limits bandwidth and scalability.

Fortunately, the FCC has recently made a change in their regulations that allows the use of a single spectrum by more than one party. Therefore, the goal of our project is to design and implement a system that can gather information about the spectrum and how to reuse it.

In our project, we will focus on the GSM and CDMA spectrums. We will implement a system that can utilize open channels in this spectrum. Moreover, we will attempt to design a system where a number of devices can utilize the same spectrum without causing interference to fellow users. Presently in the research community, there is a lot of interest in dynamic spectrum allocation, such as cognitive radio. Our project will show that fixed allocation isn't the optimal way to use the spectrum. Instead, it should be allocated dynamically. We will use COM blocks, which are cheap and light, instead of a sophisticated spectrum analyzer which is too expensive and not mobile. In conclusion, we will be taking distributed RF measurements and giving insight into proper usage.

Acknowledgement

The team would like to thank Prof. Tureli for being our Senior Design Advisor, for his incredible ideas regarding our project, and for all of his technical advice. We would also like to thank him for providing us with the lab space and lab equipment to implement our project. Last, but not least, we would like to thank Prof. Tureli's PhD student, Nilay Shah from WiNSeC, for his help and time in understanding the main objectives of our project, as well as helping us to further understand Communication Theory enabling us to have a productive Senior Design Project.

Introduction

Spectrums are divided into chunks in time and frequency. Existing spectrums have many constraints. This means that we need to find ways of sharing and reusing spectrums. One of the ways we intend to do this is through multiple access based on coding in CDMA and GSM.

CDMA (code division multiple access) is a method unlike TDMA (time division multiple access) and FDMA (frequency division multiple access). Rather, CDMA takes the original base-band signal and spreads it over a wide range of frequencies using a unique pseudo-noise code. This process is known as direct-sequence spread spectrum (DSSS). The transmitted signal has low power and noise-like qualities which make it hard to intercept, unless you know the unique pseudo-noise code used. DSSS allows many signals to be transmitted over the same frequencies (or channels), increasing the capacity of the bandwidth. CDMA is the basis for many cellular communication systems because of its low power spectral density and low probability of interception.

GSM (global system for mobile communication) is a type of TDMA developed in 1982 by a French group hosted by CEPT. GSM uses TDMA and encryption systems to make data transferring secure. GSM is the most common global standard for cellular communication. GSM operates in the 900 MHz and 1800 MHz bands while CDMA operates in the 800 MHz and 1900 MHz bands.

By implementing these techniques, the spectrum can be shared by having devices to operate alongside licensed services on a localized basis. Furthermore, in order to avoid noise interference, the devices will have to operate on a low-power basis. This is called spectrum underlay. Another method focuses on the use of unutilized channels in licensed spectrums. This involves monitoring the spectrum for these unused channels and transmitting signals over them.

First, we will search for unutilized channels. Then, we will use these channels to transmit data. Signals will be embedded into the existing spectrum through multiple networked receivers at a low signal to noise ratio. By using multiple receivers, interference can have a distorting effect on the signal. Therefore, algorithms will be used to reduce the effect of interference on the system. We will also incorporate work done by a previous senior design group that incorporated the aspect of spectrum sharing through the 802.11 protocol.

Design Requirements:

Design Objectives:

The requirements of our project are to share and reuse the spectrum in an efficient way. There are two major phases of this project. The first part of the project involves monitoring the spectrum for free and unused channels.

The second phase of our project will involve analyzing the received signals from the COM blocks to be able to suggest a more optimal way to utilize the spectrum.

System Parameters:

The hardware and software used in this project along with their specifications are as follows:

Software: MATLAB—Version 7.0: estimated lines of code: 2000

Hardware: A computer with the following configurations:

Intel® Xeon™ Processor 2.80GHz, 1MB L2 Cache

Microsoft® Windows® XP Professional SP2 with media

1GB, DDR2 SDRAM Memory, 400MHz, ECC (2 DIMMS)

80GB SATA, 7200 RPM Hard Drive with DataBurst Cache™ without RAID

Receiver Setup:

1. COM-3005 800 - 1000 MHz Receiver

• Designed for cellular and unlicensed ISM band

• Dual 10-bit A/D Converters, 40 Msamples/s

2. COM-8002 High Speed Data Acquisition

• 1 Gbit/s Maximum Data Acquisition

• Maximum sampling rate 50 MHz

• Sample Precision from 1 to 20-bit wide.

• 256 Mbytes Storage

3. COM-5001 LAN/IP Network Interface

• High Speed Network Interface for Data Transfer, Monitoring and Control of

Comblock Assembly.

Design Constraints:

While working on this project during this semester we encountered a number of problems that hindered us from achieving more success than we did. First, we didn't have a clear understanding of our project goals. Our initial objective was too involved for our knowledge. We tried very hard to do research, to understand, and to make it work, but, instead, we had to scale back a little. Therefore, we didn't start work on our actual project as early as we hoped for.

Secondly, we have been trying to gain access to the laboratory, but we haven't received our keys yet. It has been almost three weeks since we requested a copy of the key, but we haven't received any notice. This poses a problem because even if we wanted to go into the lab to analyze our signals, we couldn't.

One of the most significant constraints that might continue into next semester is the high learning curve involving programming communication theory in Matlab. The code is quite involved and in order to write code using GSM and CDMA we need to be avid in the Matlab language.

Lastly, last year's group focused on the 802.11 protocol. This year we are focusing on GSM and CDMA. We still don't have the appropriate equipment. The COM blocks are being ordered and hopefully we will have them by the beginning of next semester so that we can immediately start receiving and analyzing our data.

System Design:

To achieve the first phase of our project, we came to the conclusion that we will be monitoring the GSM and CDMA for free channels. Due to the FCC regulations we will be able to monitor licensed bands for unused channels but not transmit on these channels by using the approaches described below.

Whether it is a licensed or unlicensed band we intend to monitor the spectrum through our COM block setup. The COM block will provide us with a simple interface for our system. It will enable us to collect information from anywhere on campus and measure the utilization of spectrum for a particular provider. Moreover, through matlab coding, we will then be able to generate graphs at specific frequencies corresponding to the existing spectrum. These graphs will then enable us to determine which channels are free to transmit data on. The portability of the COM blocks will allow us to set up receivers in various locations to gain a three dimensional picture of spectrum use.

COM block Receiver Block Diagram:

Financial Budget:

Materials and Parts: Budget:

Receiver COM block Assembly:

RF Receiver--COM3005 $345

High Speed DAQ--COM8002 $345

Network Interface--COM5001 $295

Computers and Laptop $0

Development Software (Matlab) $0

Test Equipment:

Tektronix WCA230A

Wireless Communication Analyzer $23,000

Labor Cost:

4 Engineers working at $20.00 per hour per person

Each engineer working 4 hrs a week for 28 weeks

$2240 per engineer

Total Labor Cost: $8960

Total Financial Budget $32,945

Project Schedule:

Task Duration # of Days Start Date End Date

Research Project Ideas 7d Mon 9/5/05 Tue 9/13/05

Project Advisor Form 7d Mon 9/5/05 Tue 9/13/05

Preliminary Research 24d Mon 9/5/05 Thu 10/6/05

Communication Theory 10d Mon 9/5/05 Fri 9/16/05

Components-Comblocks 7d Mon 9/12/05 Tue 9/20/05

Spectrum Sharing 7d Tue 11/1/05 Wed 11/9/05

Meeting With Advisor 1d Mon 9/5/05 Mon 9/5/05

Meeting with Grad Student 2d Mon 11/21/05 Tue 11/22/05

Project Research 12d Mon 9/5/05 Tue 9/20/05

Design Approach 7d Mon 11/14/05 Tue 11/22/05

Design Selection 5d Mon 11/21/05 Fri 11/25/05

Finalize Project Design 1d Mon 11/21/05 Mon 11/21/05

Website Design 7d Tue 10/25/05 Wed 11/2/05

Project Proposal 7d Wed 10/5/05 Thu 10/13/05

Final Report-Fall 10d Mon 11/21/05 Fri 12/2/05

Final Presentation-Fall 7d Wed 11/23/05 Thu 12/1/05

Group Meetings 14d Mon 9/12/05 Thu 9/29/05

** A gantt chart is attached at the end of this report **

Task Distribution:

Christian Budiarjo—Physics and Electrical Engineer

Ø Spectrum/COMblock/Protocol Research

Ø Final Report

Ø Final Presentation

Kristen Daly—Math and Electrical Engineer

Ø Spectrum/COMblock/Protocol Research

Ø Website Design

Ø Final Presentation

Michelle Teixeira—Physics and Electrical Engineer

Ø Spectrum/COMblock/Protocol Research

Ø Final Report

Ø Final Presentation

David Toner—Physics and Electrical Engineer

Ø Spectrum/COMblock/Protocol Research

Ø Final Report

Ø Final Presentation

Conclusion:

Spread spectrum technology has become very popular and widespread in wireless communications. In particular, CDMA and GSM are both efficient technologies that allow multiple users to access unutilized channels in a given spectrum. With both these protocols each user has their own spreading codes which reduce interference. Our project aims to achieve these goals which are extremely vital to our ever-growing technology. It increases the efficiency of spectrum use. This project also analyzes all channels in the spectrum and provides a response as to which channels are available. This allows users to transmit signals achieving spectrum reuse. For example, in CDMA approximately only 20% of the spectrum is actually used. This leaves approximately 80% free channels that are available for transmission. Therefore, this project is definitely a feasible and profitable venture that will prove to be a boost for the communications industry by allowing maximum exploitation of resources.

References:

Books:

Haykin, Simon. Communication Systems 4^thed. New York: John Wiley & Sons

Inc., 2001.

Stremler. Introduction to Communication Systems 3rd ed. Prentice Hall

Electronic sources:

COM Block. www.comblock.com

http://www.comblock.com/com8002.htm

http://www.comblock.com/com5001.htm

http://www.comblock.com/com3005.htm

http://www.commsdesign.com/printableArticle/www.eet.com/showArticle.html

Senior Design Group 5 – Stevens Inst of Tech – 2003-2004