Ad-Hoc UAV Ground Network

Alternative Technology Analysis

22 May 2004

Prepared by:

Bruce R. Ward

University of Colorado at Boulder

Phone: 303-443-1466

E-mail:

CONTENTS

1.0INTRODUCTION...... 1

1.1Ad-Hoc UAV Ground Network (AUGNet)...... 1

1.1.1Limitations of Communications Equipment .....1

1.1.2Interest of DOD in COTS Equipment...... 1

1.2Emerging Wireless Communication Technologies...... 3

1.3Thesis...... 5

1.4Methodology...... 6

2.0IEEE 802.11b: BASELINE OF PERFORMANCE...... 7

2.1IEEE 802.11b Standard Overview...... 7

2.2Advantages of 802.11b Equipment for AUGNet...... 10

2.3Limitations of 802.11b Equipment for AUGNet...... 11

3.0DISCUSSION OF IEEE 802.16A TECHNOLOGY...... 13

3.1Analysis of 802.16a Standard...... 13

3.1.1802.16a Protocol Architecture...... 14

3.2General Capabilities of 802.16a Standard...... 17

3.2.1802.16a MAC Layer...... 17

3.2.2802.16a Physical Layer...... 18

3.3Security Features of 802.16a Standard in Mesh Mode...... 20

3.4802.16A Ability to communicate Peer-to-Peer...... 22

3.5State of IEEE 802.16A Standard...... 24

3.6State of IEEE 802.16A Hardware...... 25

4.0DISCUSSION OF IEEE 802.15.3 TECHNOLOGIES...... 26

4.1Analysis of 802.15.3 Standard...... 26

4.1.1802.15.3 Protocol Architecture...... 27

4.2General Capabilities of 802.15.3 Standard...... 29

4.2.1802.15.3 MAC Layer...... 29

4.2.2802.15.3 Physical Layer...... 30

4.3Security Features of 802.15.3 Standard...... 31

4.4802.15.3 Ability to communicate Peer-to-Peer...... 32

4.5Analysis of 802.15.3a Physical Layer...... 32

4.6Analysis of 802.15.3a DS IR-UWB Proposal...... 34

4.6.1Conventional IR-UWB...... 34

4.6.2802.15.3a DS IR-UWB...... 34

4.7General Capabilities of 802.15.3a DS IR-UWB Proposal....36

4.8State of 802.15.3 and 802.15.3A Standards...... 37

4.9State of 802.15.3 and 802.15.3A Hardware...... 37

CONTENTS (continued)

5.0COMPARISON OF 802.11B, 802.16A, 802.15.3, and 802.15.3A..39

5.1Comparison at MAC Layer...... 39

5.2Comparison at Physical Layer...... 39

5.3State of Standards, Compliance and Availability...... 42

5.4Limitations of 802.16A, 802.15.3 and 802.15.3A...... 42

6.0Conclusion...... 44

7.0REFERENCES...... 46

LIST OF FIGURES

FigureTitlePage

1Two Broad Classes of Test Bed Scenarios...... 2

2802.11b Protocol Architecture...... 7

3802.11b Non-Overlapping Channels: North America...... 9

4802.16a Scope of the Standard...... 14

5802.16a Data Link and Physical Layers...... 14

6802.16a OFDM Waveforms for 20 MHz Channels of Table 3....20

7802.16a WiMax Timeline for Equipment Deployment ...... 25

8802.15.3 Piconet Topology with Piconet Controller (PNC)...... 26

9802.15.3 Protocol Architecture and Scope of the Standard...... 27

10802.15.3 Frame Format for the Physical Layer...... 29

11FCC Spectral Mask for UWB Communication Devices...... 33

12802.15.3a PHY: Modulation within Transmission System...... 35

13802.15.3a PHY: Processing Steps at Transceiver System...... 35

LIST OF TABLES

TableTitlePage

1802.11b Available Channels...... 9

2UNII Licensed Exempt Band 5.150-5.850 GHz...... 13

3Available Channels UNII Band: USA, Europe...... 19

4802.16a: Raw Data Rates (Mbps) for 10 MHz Channels...... 19

5802.16a: Raw Data Rates (Mbps) for 20 MHz Channels...... 19

6802.15.3: Available Channels and Plan Types...... 28

7802.15.3:Priority Scheme with 8 QoS Priority Levels...... 30

8802.15.3:Techniques to Mitigate Interference...... 30

9802.15.3 Modulation, Coding and Data Rates 2.4 GHz PHY....31

10802.15.3aFEC Code Types and Coding Rates...... 36

11Comparison of 802.11b, 802.16a, 802.15.3, and 802.15.3a...... 40

APPENDICES

APPENDIX A – 802.16A SERVICE PRIMITIVES MESH MODE...50

APPENDIX B – 802.16A MAC PDU AND MESSAGE FORMAT....54

APPENDIX C – 802.16A PMD BURST FRAME FORMAT...... 60

APPENDIX D – 802.16A MESH FRAME STRUCTURE...... 61

APPENDIX E – 802.16A NETWORK ENTRY: MESH MODE...... 63

APPENDIX F – 802.16A MESH DISTRIBUED SCHEDULING....66

APPENDIX G – 802.15.3 SUPERFRAME...... 72

Abstract

The IEEE 802.16a, 802.15.3 and 802.15.3a DS IR-UWB wireless standards have been examined at the MAC and PHY layers and compared to the 802.11b standard to determine the possible benefits and limitations of their use in the tactical battlefield environment. The state of the alternative technology standards has been examined. Organizational support for interoperability and standards compliance among vendors has also been reviewed, as well as hardware availability.

TheIEEE 802.16a, 802.15.3 and 802.15.3a DS IR-UWBalternative technologies provide enhanced wireless communication capability in terms of the multiple access method employed, QoS support for voice, video and data services, enhanced security features for secure communication, coexistence-interference capability, available bandwidth, number of channels, bandwidth per channel, bit rate per channel, FEC and robustness to channel impairments.

In a tactical battlefield environment, the 802.16a standard is limited by fixed peer-to-peer communication in Mesh mode. However, enhancements for mobility using the basic capabilities of the MAC and Physical layers of the 802.16a standard are being developed in the 802.16e standard.

The 802.15.3 and 802.15.3a standards are limited in range by the low power requirements for operation in the ISM band and the -41.3 dBm/MHz FCC requirements for UWB device emissions in the 3.1-10.6 GHz bands. Lifting the stringent requirements for emission levels above the -41.3 dBm/MHz, in the 3.1-10.6 GHz frequency band, will allow the possible use of IR-UWB for WLAN applications.

The 802.16a and 802.15.3 standards have been approved and standardized equipment is expected to become available for commercial use during the 2nd half of 2004. Approval of the 802.15.3a enhanced Physical standard is not expected until 2005 or later. The WiMax and WiMedia organizations provide support for interoperability testing and standards compliance. These organizations will ensure the development of low-cost 802.16a and 802.15.3 COTS equipment.

Section One provides an introduction to the battlefield environment, an overview of 802.11b wireless local area network (WLAN) technology, as well as a description of the Thesis and Methodology for the document. Section Two provides an overview of the 802.11b standard which is used as the baseline of performance. In addition, Section Two also describes some of the benefits and disadvantages of using the 802.11b technology in the battlefield environment. Section Three discusses the 802.16a wireless metropolitan area network (WMAN) technology, the state of the 802.16a standard and the state of 802.16a standardized hardware. Section Four details the 802.15.3 wireless personal area network (WPAN) technology. Section Four also analyzes an amendment standard proposal for the 802.15.3 Physical Layer using direct sequence impulse response ultra-wideband (DSIR-UWB) that provides for higher bandwidth and data rates. In addition, section Fourdescribes the state of the 802.15.3 and 802.15.3a standards as well as the state of the hardware. Section Five gives a comparison of the 802.11b, 802.16a, 802.15.3, and 802.15.3a standards technology. Section Six provides a conclusion.

1

1INTRODUCTION

1.1Ad-Hoc UAV Ground Network (AUGNet)

The tactical battlefield communication environment is a dynamic, hostile, and constantly changing environment. Tactical units deployed within the battlefield environment in support of a mission consist of mobile ground troops and ground support vehicles, as well as unmanned aerial vehicles (UAV’s) to maintain communication coverage. Communication of mission critical voice, video and data among tactical unit members and operations centers is implemented through the formation of mobile wireless ad-hoc (peer-to-peer: mesh) networks with the ability to dynamically form communications networks without pre-existing communication infrastructure.

Ground troops and support vehicles equipped with communication radios as well as radios placed at fixed site locations within the network form the ground nodes of the ad-hoc network. In general, communication routes between source and destination ground nodes may include multiple hops using intermediate nodes to relay traffic from source to destination when the nodes are not in direct communication range of each other.

When ground nodes become separated by distance or geography (such as hills or obstructions) the network becomes disconnected. In these situations, the UAV equipped with communication radios serves as a communication gateway - relay node between disconnected nodes on the ground. Ground nodes that are isolated from each other can reach each other through the UAV. The UAV‘s are placed at high altitude to act as a line of sight communication relay node for the tactical unit ground nodes. Using the UAV as a communication relay node enables two-hop transmission between any pair of ground nodes in the area using the UAV as a relay router.

The UAV may also function as a communication gateway to operation and data centers via other UAV’s and communication satellites.

1.1.1Limitations of AUGNETCommunications Equipment

Wireless communication radios used in mobile ad-hoc networks within the battlefield environment have been specialized radios utilizing designated military bands. Proprietary equipment based on military standards has been used to implement proprietary architecture and protocols at the Media Access Control (MAC) Layer and the Physical Layer. Although there are imposing military specifications for equipment, equipment vendors developing the proprietary equipment are not subjected to commercial standard specifications and interoperability requirements. Radio development, procurement and cost aremore dependent upon agreements with specific vendors, which enable vendors to maximize profit in a less than competitive environment.

1.1.2Interest of DOD in COTS Equipment

Recently, the Department of Defense (DOD) has become interested in analyzing the performance capabilities of commercial off the shelf (COTS) wireless local area network (WLAN) equipment. In particular the DOD is interested in the use of COTS equipment based on the IEEE 802.11b standard, for the tactical battlefield environment.

At the NavalPostGraduateSchool, a series of experiments are being conducted to investigate the use of WLAN’s for both ground units and unmanned aerial vehicles in a tactical battlefield environment. The Surveillance and Target Acquisition Network (STAN) team in conjunction with the Sierra Nevada Corporation have conducted successful initial experiments using COTS 802.11b standardized equipment. The goal of current experiments is to improve the network and allow for greater network expansion. [27, 28]

During the fall of 2003 the COMCEPT division of L-3 Communications Corporation engaged the University of Colorado to design, install and operate a wireless communication testbed. The goal of the testbed is to demonstrate the performance capabilities of COTS radios in battlefield scenarios using low-cost WLAN 802.11b technology, combined with low-cost UAVs. Two broad scenarios shown in Figure 1 will be used in the testbed plan. [27, 28]

In a tactical battlefield environment, 802.11b technology has certain benefits and limitations as will be discussed in Section 2.

1.2Emerging Wireless Communication Technologies

Currently, there are new technologies on the horizonthat may improve-enhance communication within the tactical battlefield environment.The IEEE 802.16a and IEEE 802.15.3 wireless communication standards represent two of these new and alternative technologies. The IEEE 802.16a standard has been developed for communication in Wireless Metropolitan Area Networks (WMAN’s) and the IEEE 802.15.3 standard has been developed for use in Wireless Personal Area Networks (WPAN’s). These standards utilize new protocol architectures at the MAC and Physical layers.

Motivation for choosing the IEEE 802.16a standard

The IEEE 802.16astandard developed for WMANs supports peer-to-peer communication in mesh mode within the 5.1-5.85 GHz UNII band. The standard uses TDMA for multiple-access. Service to an individual node is based on a grant-request MAC.

The grant-request MACwas developed to provide QoS support for voice, video and data through the use of guaranteed time slots and priority levels of service. In addition, the 802.16a MAC was designed to support thousands of users and mitigate interference in the license exempt UNII band through the use of Dynamic Frequency Selection (DFS).

At the MAC layer, the 802.16a standard also provides enhanced security features through the use of the Privacy Key Management (PKM) protocol. The PKM protocol is used to authenticate candidate nodes, establish and manage shared secret keys between nodes, encrypt and authenticate messages, and encryptand decryptdata.

At the Physical layer, the 802.16a standard was designed for an outdoor non line-of-sight (NLOS) environment covering multi-mile distances. As a result, the physical layer is capable of handling greater multi-path delay spreads than found in an indoor environment without the use of an equalizer.

The IEEE 802.16a physical layer also provides a larger number of available channels for operation than 802.11b. Channel bandwidth can be scaled to accommodate 10 MHz and 20 MHz channels. Within each channel, rate adaptive modulation allows for the use of 18 different data rates based on link conditions and service needs. Using the 802.16a standard, bandwidth efficiency can also be increased

Motivation for choosing the IEEE 802.15.3 standard

The IEEE 802.15.3 standardis a new specification designed to provide high data rate (HR) services for wireless personal area networks (WPAN)’soperating in the ISM band. The standard supports peer-to-peer communication.

Like 802.16a, the 802.15.3 standard uses TDMA for multiple-access. Service to an individual node is based on a grant-request MAC using a piconet network controller (PNC) that provides the basic timing for the network, grants network access, allocates resources, and manages QoS requirements.

The 802.15.3 MAC was developed to provide support for multi-media services. QoS support for voice, video and data is provided through the use of guaranteed time slots, with slot widths based on priority levels of service. Interference mitigation in the license exempt ISM band is accomplished through the use of Dynamic Frequency Selection (DFS).

At the MAC layer, the 802.15.3 standard also provides enhanced security features to authenticate candidate nodes, establish and manage shared secret keys between nodes, encrypt and authenticate messages, and encrypt and decrypt data.

At the Physical layer, the 802.15.3 standard was designed for a fixed or mobile non line-of-sight (NLOS) environment covering 10 meters to 70 meters. The standard provides for the use of four 15 MHz channels using single carrier modulation. Within each channel, rate adaptive modulation allows for the use of five different data rates varying from 11 Mbps to 55 Mbps to handle multi-media services such as high definition video, audio and bulky data transfers.

The IEEE 802.15.3a amendment standard

An amendment standard IEEE802.15.3a (not yet ready for publication) is currently being developed to enhance the 802.15.3 Physical layer and provide very high data rates up to 480 Mbps. With the increased data rates, the IEEE 802.15.3a Physical layer will support applications such as wireless video projection, video conferencing, image transfer, and high speed cable replacement.

Why Not 802.15.1 Bluetooth?

The 802.15.3 WPAN standard was chosen for use in the AUGNet environment over the 802.15.1 Bluetooth standard based on the larger number of allowable devices in the network, the faster network connection time, the shorter transmit-to-receive turnaround time, and the support for multi-media QoS.

Using 802.15.1, only seven devices can operate in a network (piconet) under the control of a PNC as compared to 256 devices for 802.15.3. As the number of nodes increases, the bluetooth network must be divided into 8 node chunks. Broadcast communication is only available within a network of up to 8 nodes.

In terms of network connection time, a Bluetooth device is not capable of joining a network rapidly which reduces the ability to communicate in a mobile ad-hoc network. Network connection time can take up to 5 seconds as compared to an 802.15.3 device which has a network connection time much less than one second.

In a mobile ad-hoc network fast switching is important to receive and transmit packets quickly as the network is dynamic and constantly changing. The 802.15.1Bluetooth standard provides a transmit to receive turnaround time of less than 250 microseconds as compared to 10 microseconds for devices based on the 802.15.3 standard.

Finally, the 802.15.3 was chosen over the 802.15.1 Bluetooth as it provides support for multi-media QoS via increased bandwidth, data rates, and guaranteed time slots with slot width based on priority. The 802.15.1 standard can only provide a bit rate of 1 Mbps using 79 Frequency hopping channels of 1 MHz each, with no guaranteed time slots based on priority.

1.3Thesis

The goal of the alternative technology research document is to show that the IEEE 802.16a, IEEE 802.15.3, and 802.15.3a wireless communication standards have the potential to represent viable commercial off the shelf (COTS) alternative technologies to 802.11bthat can enhance communication within the Ad-hoc UAV Ground Network tactical battlefield environment.

Communication in the AUGNet tactical battlefield environment can be enhanced using the IEEE 802.16a, IEEE 802.15.3 and IEEE 802.15.3a standards through quality of service provisions, improved security features, increased available bandwidth and data rates,interference mitigation, and increased robustness to multi-path delay spread.

The 802.16a and 802.15.3 standards have been approved and standardized equipment is expected to become available for commercial use during the 2nd half of 2004. Organizational support for interoperability testing and standards compliance will ensure the development of low-cost COTS available equipment.

1.4Methodology

The AUGNetalternative technology research document will support the thesis through analysis of IEEE standard specifications, published journals, articles, and reports generated by organizations endorsing the standards. Specifically, the document will analyze and discuss the following key areas:

  1. Overview-Analysis of IEEE 802.11b wireless communication standard
  2. Advantages of 802.11b equipment in an AUGNet environment
  3. Limitations of 802.11b equipment in an AUGNet environment
  1. Description- Analysis of IEEE 802.16a , 802.15.3 and 802.15.3a wireless communication standards
  1. Architecture- Protocol Stack
  2. Data Link layer (MAC layer)
  3. Physical layer
  4. General capabilities of the IEEE 802.16a, 802.15.3 and 802.15.3a standards at the MAC and Physical layers
  5. Security features associated with the standards
  6. Ability of the standards to support peer-to-peer communication
  1. Discussion of the current state of 802.16a, 802.15.3 and 802.15.3a standards
  1. Timelines for standard approval
  2. Organizations created to endorse the standards and the role of the organizations
  3. Companies supporting the standards
  1. Discussion of the current state of 802.16a, 802.15.3 and 802.15.3a standardized hardware (available now, next quarter, etc.)
  1. Timelines for hardware deployment
  2. Companies involved in hardware production and deployment
  1. Comparison of the 802.11b, 802.16a, 802.15.3 and 802.15.3a standard technologies

Through this analysis, we will examine the potential of the IEEE 802.16a, IEEE 802.15.3, and 802.15.3a wireless communication technologiesfor use as COTS alternative technologies in the AUGNet tactical battlefield environment. In addition, the analysis will help determine whether the new technologies can improveon quality of service, security, available bandwidth and data rates, interference mitigation and robustness to channel impairments.

2ieee 802.11B:Baseline of Performance

As indicated in Section 1.1.1, the wireless communication testbeds developed at the NavalPostGraduateSchool and the University of Colorado are being used to examine the performance of 802.11b technology in tactical battlefield scenarios. These wireless communication testbeds, represent two examples of the DOD’s current interest and ongoing desire to test the capabilities of 802.11b standardized equipment in the battlefield environment.

Based on the current interest of the DOD in 802.11b, and the development of the two wireless communication testbeds, the AUGNet alternative technology research document will use the 802.11b technology as the baseline of performance for comparison of the emerging IEEE 802.16a, 802.15.3 and 802.15.3a wireless communication technologies.