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Trends in Broadband Wireless Communication Systemsand Software Defined Radios

Kazuhiro UEHARA

NTT Network Innovation Laboratories, NTT Corporation,

1-1 Hikari-no-oka, Yokosuka 239-0847, JapanE-mail: [email protected]

Received February 20, 2006; final version accepted April 30, 2006

Next generation wireless communication systems require a higher broadband performance to support highlyrealistic rich content and still be capable of seamlessly supporting integrated services using a variety of differentnetwork access systems. This paper reviews the current trends in broadband wireless communication systems,including cellular, wireless LAN, and fixed wireless access (FWA) systems. Furthermore, we describe the recentactivities in the development of software defined radios (SDRs) that are essential for realizing the systems beyond3G, with a particular focus on processor and security issues.

KEYWORDS: beyond 3G, WLAN, FWA, software defined radio, reconfigurable processor

1. Introduction

At the end of 2005, there were 80 million Internet users in Japan, which represents 62% of the population. There

were 20 million broadband users, accessing from ADSL, fiber to the home (FTTH), and CATV. In 2005, the number of

FTTH subscribers exceeded CATV. As for the number of increases, FTTH passed ADSL in the first quarter of the year.

According to the International Telecommunication Union (ITU) representatives in a paper on The Portable Internet,

the broadband service fee in Japan is the lowest in the world. The number of 3G subscribers is 41 million. The total

number of cellular and PHS subscribers is 94 million, which increased 10 times in 10 years. Todays users expect more

advanced broadband wireless access in their homes and offices, and even in mobile environments.

Figure 1 shows the trends in wireless communication systems. In June 2003, the ITU Radiocommunication Sector

(ITU-R), Study Group 8, Working Party 8F (WP8F) formulated the recommendation M.1645 [1]. This recommendationcontains a vision that gives direction to future technologies for the future development of 3G systems and also describes

new capabilities for systems beyond 3G. The objectives are to develop a system for anytime, anywhere, and anyone.

These systems beyond 3G will include higher data rates, improved roaming, and true inter-system mobility

management. With a projected timeline of around 2010, the data rate goals were set at 100 Mbit/s for high mobility

systems, such as mobile access, and up to approximately 1 Gbit/s for low mobility systems, such as nomadic wireless

access (NWA).

The systems beyond 3G will be designed by combining several access technologies that will complement each other

to meet the various service requirements and radio environments and to provide a common and flexible service

platform. Various access systems, such as 3G cellular, new high-speed systems, WLANs, and short-range radios, will

be connected using a flexible core network. Users can be connected from a variety of different access systems to the

networks and services. A seamless inter-working between these different access systems in terms of horizontal and

Mobility

High

Low

bit/s1M 10M 100M100k 1G

3.5G.5G(2 GHz)

IMT2000

WLANLAN(2.4 GHz/5 GHz)

~384k384k

3GG(2 GHz)

EVDOHSDPA

~2.4M/14M2.4M/14M

2GG(800 MHz

1.5 GHz)

PDCGSM

~9.6k/9.6k/28.8k8.8k

PHS

~64k/64k/128k28k

2MM11M1M54M4M

4GG

>100M00M@MACSAP

Nextext GenerationenerationWLANLAN

FWAWA~80M80M

Next Generation FWAext Generation FWA>100M00M

Fig. 1. Trends in wireless communication systems.

Interdisciplinary Information Sciences, Vol. 12, No. 2, pp. 163172 (2006)


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vertical handover and seamless service provision with service negotiation, including mobility, security, and QoS

management, is essential. Unified radio interfaces will not likely be capable of covering all the requirements and

demands of future mobile communication networks. Consequently, multi-mode and multi-band infrastructures and

terminals will also be essential for the systems beyond 3G, and software defined radio (SDR) could be a key technique

for realizing these objectives [2].

In Section 2, we review the trends in broadband wireless communication systems including cellular, wireless LAN,

and fixed wireless access (FWA) systems. In Section 3, we describe recent activities in the development of software

defined radios (SDRs), which are essential for realizing the systems beyond 3G, with a special focus on processor andsecurity issues.

2. Broadband Wireless Communication Systems

2.1 Cellular

As a 3.5G system, High Speed Downlink Packet Access (HSDPA) will be used to start the service in March 2006.

The system can achieve a transmission speed of up to 14 Mbit/s, even when using the same 5 MHz frequency

bandwidth as W-CDMA.

For next generation systems, a very high-speed wireless access of approximately 1 Gbit/s is required. One possible

technology that satisfies the requirements is Variable Spreading Factor Orthogonal Frequency and Code Division

Multiplexing (VSF-OFCDM) [3]. This is based on multi-career CDMA (MC-CDMA) technologies and it uses a

variable spreading factor scheme to increase the system capacity. A successful experiment performed by NTTDoCoMo achieved 1 Gbit/s real-time packet field transmission combined with MIMO technology in June 2005 [4].

So far, a lot of attention has been paid to MC-CDMA as a promising wireless access technique. However, recently it

has been shown that direct sequence CDMA (DS-CDMA) can achieve a good performance compared to MC-CDMA if

a proper frequency-domain equalization scheme is adopted [5].

2.2 Wireless LAN

Figure 2 shows the trends in IEEE 802.11 wireless LANs. The original IEEE 802.11 standard was established in

1997 and uses the 2.4 GHz ISM band, which had a data rate of 2 Mbit/s. In 1999, 11a and 11b were standardized. The

2.4 GHz 11b system has backward compatibility with the original system. Currently, the 11b system is the most popular

system in the world, and 11a is a 5 GHz system with a high bit-rate of 54 Mbit/s, which was realized using OFDM

technology. In 2003, 11g, with a bit rate of 54 Mbit/s was established. It uses OFDM technology in the 2.4 GHz band

and has backward compatibility with the 11b system. Currently, a new standard, 11n, is being studied by task group N.

The purpose of the task group is to standardize new high throughput wireless LANs, with a MAC-SAP throughput of

more than 100 Mbit/s. The key technologies used were MIMO in PHY layer and frame aggregation technology in

MAC layer [6].

2.3 FWA, WMAN

The Wireless IP Access System (WIPAS) is a fixed wireless access (FWA) system in the 26 GHz band. Figure 3shows a service image of WIPAS, and the main specifications are given in Table 1. This WIPAS system is based on a

combination of optical and wireless technologies and provides broadband access rapidly at low cost. WIPAS is

2

1999 2001 20031997 2005

11

Mbit/s 54

>100

2007

5 GHz

2.4 GHz

DS/FH/IR

CCK

OFDMMIMO

OFDM

Year

TGe QoS supportTGi Enhanced securityTGr Fast roamingTGs Mesh network802.11

802.11b

802.11g802.11a

802.11n

Fig. 2. Trends in IEEE 802.11 WLAN.

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expected to become an efficient tool for solving the regional-based digital divide problem and overcoming theinstallation difficulties of optical fibers in metropolitan area apartment buildings. An access point (AP) is attached to a

telephone pole and can cover about 1 km. The AP is connected to an IP network using optical fiber. A wireless terminal

(WT) is attached to the users home. The maximum radio transmission rate is 80 Mbit/s and the maximum Ether frame

transfer rate is 46 Mbit/s. An adaptive modulation scheme is used to maintain the radio link by controlling the

transmission rate [7]. NTT is now promoting WIPAS applications for multiple-unit housing, such as apartments, and

for detached houses in new residential areas, and for municipal intranets that can exploit local expansion.

The IEEE 802.16 WG on broadband wireless access standards is developing standards and recommendations to

support the development and deployment of broadband wireless metropolitan area networks (WMANs). The system is

known as worldwide interoperability for microwave access (WiMAX) and the typical coverage area is about 5 km from

the base station and the maximum speed is 75 Mbit/s. In reality, the coverage and speed depend on the environment in

which the system is used and on that particular systems configuration [8]. Several standards were used to achieve this.

IEEE 802.16-2004 was adopted in June 2004 and implemented in FWA and NWA services. Then, IEEE 802.16e wasapproved in December 2005 and supports portable and mobile uses, in addition to fixed and nomadic access uses [9].

2.4 WPAN

Another broadband system, ultra wideband (UWB) is currently under discussion in IEEE 802.15 [10]. This is

included in wireless personal area networks (WPANs), which are used more for short-range communications than

WLAN. The IEEE 802.15.3a is a UWB specification. It uses a frequency bandwidth of more than 500 MHz, or more

than 20% of the relative frequency bandwidth. The frequency band is from 3.1 to 10.6 GHz. The data rates and ranges

are 110 Mbit/s for more than 10 m, and 200 Mbit/s for more than 4 m (480 Mbit/s for less than 5 m). The UWB system

will feature a very high-speed and low power consumption in short-range communications.

3. Software Defined Radio

3.1 SDR features

Recent technical progress and cost-reductions in digital signal processing devices and urgent demands for seamless

Fig. 3. WIPAS service image [7].

Table 1. Main Specifications of WIPAS [7].

Item Specification

Frequency band 26 GHz

Modulation scheme QPSK/16QAM Adaptive

Transmission scheme TDM/TDMA/TDD

Ethernet frame transfer rate QPSK: 23 Mbit/s, 16QAM: 46 Mbit/s

Number of accommodated WTs Maximum of 239 WTs per AP

QoS control Fairness assignment employed among WTs

Trends in Broadband Wireless Communication Systems and Software Defined Radios 165


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mobile communications are driving the research and development of software defined radio (SDR), which enables a

single terminal to handle various kinds of wireless systems through a simple software change to reconfigure the

terminals functions. Its application areas include military uses, home networks, intelligent transport systems (ITS), and

broadcasting, in addition to cellular communications. The SDR terminal is constructed using programmable devices,

such as digital signal processors (DSPs) and field programmable gate arrays (FPGAs), and uses multiband radio

frequency (RF) circuits (Fig. 4).

Figure 5 illustrates some future possibilities that could be enabled using SDR technology. Seamless communication

could be possible by selecting the wireless system that best corresponds to the communication environment and users

requirements. Users can access the best system available. Overseas travelers simply download the system software of

the host country. Moreover, the desired quality of service can be maintained while improving service economy based

on the data-rate and communication fee [11]. Over-the-air software downloading lets you upgrade your terminal as new

functions become available or when bug-fixes are released, even when you are at home. SDR technology is also very

attractive for operators. Usually, upgrading or debugging the enormous number of cellular base stations is a labor-

intensive task that involves a huge amount of manpower. However, SDR base stations can be remotely debugged

quickly by downloading new software via the network. SDR technology also has benefits for manufacturers. Specific

chips no longer need to be developed for each system on extremely short notice. This means that only the software

needs to be developed, which greatly reduces development times and costs. This scheme allows new technologies to becommercially introduced much more quickly than the conventional one. Therefore, it may be possible to reduce the

recent shortage of frequency resources by quickly using future technologies and systems that have greater spectral

efficiency.

3.2 SDR research and development historyTable 2 shows a historical perspective of SDR development. Research and development on SDR originally started in

the 1980s to develop a US military communication system. It was continued as a Joint Tactical Radio System (JTRS)

ProgrammableprocessorsA/D, D/ARF

ExternalI/F Data

Controller

Digital processing blocksMultiband

antenna

Download via storage media, wireless- and/orwired-communications

Multiband

RF circuits

Antenna

Software

Fig. 4. Typical SDR architecture.

Fig. 5. Possibilities enabled by SDR technology.

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project. In the 1990s, it was driven by rapid technological progress and cost-reductions in digital signal processing

devices, such as DSPs and FPGAs [12]. In 1996, the SDR Forum (formerly the modular multi-function information

transfer systems (MMITS) Forum) was established and it currently has more than 100 members, worldwide [13, 14].

The SDR architecture and program download schemes have been discussed in the SDR Forum and at many conferences

[1517]. In June 2000, Motorola announced that they had started to develop a cellular SDR terminal. In September

2001, the US Federal Communications Commission (FCC) adopted rule changes to allow the use of SDRs [18]. Thenew rules allow manufacturers and operators to reconfigure devices after they have been deployed in the field.

In Europe, studies that mainly focused on the overall perspective of reconfigurable systems were carried out in many

SDR-related co-projects, such as MMR (multi-mode multi-protocol radio), SORT (software radio technology),

PROMURA (programmable multimode radio for multimedia wireless terminals), SLATS (software libraries for

advanced terminal solutions), and TRUST (transparently reconfigurable ubiquitous terminal), under the ACTS

(advanced communications technologies and services), ESPRIT (European strategic program for R&D in information

technology), and IST (information society technologies) projects. The mobile execution environment (MExE) was

standardized in 1999, and it essentially provides the security framework to download and execute software on the

mobile terminal. The End-to-End Reconfigurability (E2R) project started in 2004 as an integrated project (IP) of the 6th

Framework Programme of the European Commission (EC), following on the themes of previous projects. The main

challenges of Phase 2 (20062007) will be to develop and demonstrate solutions for interoperability, scalability, and

flexibility to enable efficient support of ubiquitous access, pervasive services, and dynamic resource management in theradio environment of the future [19].

In 1996 in Japan, a study group for software defined receivers was organized by the Association of Radio Industries

and Businesses (ARIB) with the support of the Ministry of Post and Telecommunications (MPT) (currently, MIC:

Ministry of Internal Affairs and Communications) and the final report was completed in 1999 [20]. In December 1998,

a software radio technical group (SR-TG) was organized by the Communication Society of the Institute of Electronics,

Information, and Communication Engineers (IEICE) in Japan. The group has been very active in discussing SDR

issues, including devices, algorithms, APIs, operating systems, software downloading, regulations, and so on [21]. In

April 2000, the Telecom Engineering Center (TELEC) with support from the Ministry of Public Management, Home

Affairs, Posts and Telecommunications (MPHPT, formerly MPT, currently MIC) began three years of serious

discussions that resulted in accepting the SDR concept in the Japanese legal and regulatory environment. In March

2003, they summarized their findings in a final report entitled the Technical Regulation Conformity Evaluation

System for SDR. In December 2003, based on the results of these studies, the MPHPT invited Public Comments for

Introduction of SDR-related Regulatory Certification System. In February 2005, based on these public comments, anew regulation was adopted that allowed an SDR scheme to introduce new channels for 5 GHz wireless LANs after

May 2005.

Table 2. SDR Development History.

Year US Europe Japan

1980s Military radios

1990 SPEAKeasy program (DARPA and Air Force)

1992 J. Mitolas SDR concept

1995

Special issue of IEEE Commun. Magazine

Bellsouths (currently, Singulars) global

vision of 3G based on SDR SPEAKeasy II program

ACTS project (to 1999)

1996 MMITS Forum (currently, SDR Forum) FIRST project ARIB study group (to 1999)

1997First intl. workshop

on SDR held in Brussels

19 98 JTRS Program

1st SDR workshop in Asia

Software Radio Technical Group

in IEICE

1999SDR Forum

J. Mitolas cognitive radio conceptMExE project and 3GPP

2000 FCCs NOI TRUST project TELEC study group (to 2003)

2001FCCs rule amendment for SDR

(1st general SDR authorization in the world)

Workshop on SDR regulation (MPHPT

(currently, MIC), FCC, SDR Forum)

2002

2003 MPHPT invited public comments

2004 E2R project (to 2009)

2005 DySPAN workshopNew regulations adopted permitting SDR

scheme for 5 GHz WLAN



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3.3 SDR feasibility studies at NTT

In 1999, NTT developed the first SDR prototype that can support cellular systems such as PHS (Personal Handy-

phone System). It handled only narrow bandwidth (up to a few hundred kilohertz) wireless systems, which use the

TDMA (Time Division Multiple Access) scheme [22]. However, it could not handle wireless LAN systems that use the

DSSS (Direct Sequence Spread Spectrum) scheme because it cannot handle bandwidths of more than 20 MHz.

In November 2001, NTT announced the successful development of an improved SDR prototype that can support

both low-speed wireless systems such as PHS and high-speed, broadband wireless systems, such as IEEE 802.11wireless LAN (Figs. 6 and 7) [23]. We developed a novel wideband, flexible-rate pre-/post-processor (FR-PPP) to

overcome the bandwidth restrictions [24]. The FR-PPP consists of FPGAs and a direct digital synthesizer (DDS).

Conventional pre-/post-processors (PPPs) have preset parameter hardwired circuits including various kinds of filters to

support the targeted wireless systems. Therefore, their circuit scale is enormous. The FR-PPP is much smaller because

the FPGA can flexibly adapt to the filters required by each system. In addition, while conventional PPPs use

complicated interpolation circuits to support the various clock-rates of the targeted wireless systems, the DDS in the

FR-PPP can generate any clock-rate that is needed. This also reduces the circuit scale and offers high-speed operations.

These breakthroughs enable a wide-bandwidth and very flexible SDR that can support wireless LANs and 2G systems.

The processing power of the prototype can also support 3G systems, such as W-CDMA. We also developed a

multiband RF circuit that can cover frequency bands from 900 MHz to 2.5 GHz using direct conversion technology

[25]. In addition, over-the-air software downloading was successfully implemented. Its protocol is very general and

compact because it is based on TCP/IP and uses the physical layer of the active wireless system. To ensure that

downloads are secure, the 128-bit next-generation block cipher Camellia, which was jointly developed by NTT and

Mitsubishi Electric Corporation, was implemented in the protocol [26].

Feasibility studies showed that SDR technology will allow a single mobile terminal to cover second- and third-

generation mobile systems, as well as higher-speed and broader-bandwidth wireless systems, such as wireless LANs.However, making an SDR mobile terminal whose size, cost, and power-consumption rival those of current mobile

terminals still has issues to overcome. The processing power and power consumption of programmable processors need

CPU

External I/F

Multiband RF/IF

Control display

DSP and FR-PPP

Fig. 6. NTTs SDR prototype, which can support PHS and IEEE 802.11 wireless LAN.

ExternalI/F

DSP

CPU

VME bus

(Base St.)ISDN

(Terminal)Voice

Bearer

MMI

MultibandRF/IF

ADCDAC

FR-PPP

14-bit (D/A)12-bit (A/D)

6611 MHz

64

32

1.5/1.9/2.45 GHz

2211 MHz

Modulation/demodulation,

voice CODEC (PHS),spectrum spreading (W-LAN), etc.

Channeling, filtering, spectrum

de-spreading (W-LAN), etc.

Filter switching type

Reconfigurable

System control, MAC (W-LAN),call control (PHS), etc.

Multiband

antenna

Ethernet

Fig. 7. Block diagram of NTTs SDR prototype.

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to be greatly improved. Regulatory and security issues must also be considered to guarantee safe software downloads in

the field for services using SDR technologies.

3.4 Processor issues for mobile terminals

When mobile terminals use SDR technology, hardware miniaturization and low power consumption are required to

meet the size and power requirements. Moreover, for high-speed data transmission, such as wireless LANs, high-speed

signal-processing capability is also necessary. Current commercial general purpose DSPs and FPGAs do not satisfy

these requirements simultaneously.Reconfigurable processors have the following features: (a) dynamic reconfiguration of circuit constitution within a

few clocks, (b) homogeneous/heterogeneous constitution of multiple processor elements for high-speed parallel signal

processing, and (c) high-speed data path for high-speed signal processing. Although reconfigurable processors are

expected to be suitable for SDR mobile terminals, few studies have evaluated their performance, based on actual

wideband wireless communication systems. Therefore, to evaluate the reconfigurable processor, we developed SDR

software for an IEEE 802.11a wireless LAN baseband, one of the wideband wireless standards, and evaluated its power

consumption characteristics and high-speed signal processing features [27, 28].

There are two types of reconfigurable processors: A homogeneous type that uses multiple identical execution nodes

[29], and a heterogeneous type that uses different execution nodes [30, 31]. Although the latter requires careful

consideration of each task assigned to the node, if tasks are assigned efficiently a high signal processing performance

can be obtained using the least amount of hardware. Therefore, we focused on the heterogeneous type Adaptive

Computing Machine (ACM) reconfigurable processor [31]. The ACM processor has three kinds of nodes:

Programmable scalar nodes (PSNs), domain bit manipulation nodes (DBNs), and adaptive execution nodes (AXNs).

The PSN is a kind of a RISC processor, the DBN can perform bit-intensive algorithms efficiently, and the AXN is a

kind of parallel DSP. Each ACM chip has two PSNs, four DBNs, and four AXNs.

Figure 8 shows a developed signal processing board. The developed IEEE 802.11a software uses two prototype

ACM processors; one for transmitting and one for receiving. Furthermore, we used one processor for each of the PHY

and MAC layers. The software was assigned to the most suitable node. One task is performed on each node, and can be

changed on each clock. Each node is connected to a 32-bit high-speed data bus, matrix interconnect NW (MIN).

The measured results of the peak power consumption at a clock speed of 200 MHz were 1.6 W for the PHY layer and

1.1 W for the MAC layer. If they were implemented on one chip, the total power consumption was estimated to be

1.9 W. To evaluate the signal processing performance, we measured the latency time. To meet the IEEE 802.11a shot

inter-frame space (SIFS) specification of 16ms, the latency time should be less than 13.5ms, except for the estimated RF

processing delay of 2.5ms: The measured result was 18.9 ms. If the clock speed was increased to 280 MHz, the latency

time was estimated to match the target value, although the power consumption increased to 2.6 W. Because theprototype ACM processor was not optimized, the measured power consumption was not as low as for mobile terminals,

and the latency did not perfectly meet the specifications. However, the results show the potential of reconfigurable

processors.

3.5 SDR security issues

The introduction of SDR will trigger new security problems, unlike those faced by conventional wireless

communication systems. In Japan, the Minister of the Ministry of Internal Affairs and Communications (MIC) must

issue a license to establish a radio station. Therefore, designs cannot be changed without permission from the Minister.

In addition, because of the technical regulation conformity certification rule, the function of the radio terminal cannot

be changed after receiving certification. However, by changing the software we can change the functions of SDRs,

which creates a new set of problems. In conventional wireless communication systems, illegal actions, such asexcessively powerful radio waves and jamming are mainly done by altering the hardware. Although SDR terminal

hardware can be altered the same way as conventional radio terminals, illegal software is seen as the more serious

ACM

processor

Digital I/O

interface

Host FPGA

Fig. 8. Configuration of baseband signal processing board.



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problem. While expertise and special tools are needed to alter hardware, illegal software can be easily mass-produced

on PCs and widely distributed across the Internet. Therefore, we need new technical regulation conformity certification

rule and new security measures to realize SDR services. The use of illegal software will damage not only the radio field

but also other fields. The issues raised by the use of illegal software are summarized in Table 3. Problems with

copyright infringement are sure to arise, as are problems caused by illegal service use and viruses. Attacks that delete

important data and illegal transmissions triggered by viruses that have no effect on conventional radio systems are

predicted to strike SDR. Software defined radio faces many different threats, and so various security measures are

needed. Note that SDR is different from the Internet and computers in that SDR must comply with radio regulations.

Figure 9 shows a terminal software distribution model. This model differs from the conventional content distribution

model because the certification agency must always certify software by referencing the radio law and create evidence of

certification in all distribution channels. Because we cannot trust all users to use software legally, the first users must

distribute the software by taking appropriate security measures based on the distribution channel. Moreover, to prevent

the illegal use of services by applying techniques such as spoofing, the first users must select security measures that best

suit a particular service. Basically, a minimum level of security must guarantee the software certificate issued by the

certification agency. In addition, the carrier, service provider, and user must ensure that the necessary higher levels of

security are in place to satisfy the requirements.

Figure 10 summarizes the security architecture for SDR [32]. Security layer 1 implements the security measures in

compliance with radio law. National bodies and the certification agencies are most concerned with this layer. Layer 2shows the security measures needed to guarantee service quality and protect rights, such as copyrights. The software

maker and vendor, and the service provider, are involved with this layer. Layer 3 is executed by the user, who

implements personal security measures to protect his/her personal data and privacy. In this architecture, security layer

1 is the essential security layer and security layers 2 and 3 are executed as required, based on system design and use.

Table 3. Problems of Illegal Software.

Illegal action Method of illegal action Damage

Radio law Own software Jamming, interference

High power Alteration Malfunction

Channel occupation Virus software Decrease in service quality

Out of band use

Copyright law Copy

Income decrease Abuse of software Abuse of license

Criminal law Alteration of ID Spoofing

Abuse of a terminal Authentication/account process change Income decrease

Damag e to person al d ata Virus so ftware Data loss

Data outflow

Certificationagency

Software maker(Vendor)

First user(Content/service provider)

Purchaser(User)

DistributionChannel

Licensing

Application

Certification

AttackFalsification, abuse, illegal copy, spoofing, etc.

Fig. 9. SDR software distribution model.

- Government

(Certification agent)

- Regulatory issues

(Radio law)1

- Vendor, maker

- Service provider

- Right protection

- Service quality guaranty2

- User- Data protection

- Privacy protection3

Person in charge of securityPurpose of securitySecurity

layer

Fig. 10. SDR security architecture.

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In security layer 1, the SDR terminal works by combining software and hardware. Therefore it is essential to avoid

activating the radio terminal unless the software and hardware satisfy the following two conditions:

(1) Both software and hardware have been certified, and

(2) Software has not been tampered with.

The SDR terminals should contain functions to detect and reject software that has been tampered with before

installation on the hardware. To detect such software, we could apply an electronic signature technique. From April

2000 to March 2003, a Study Group on Software Technology for Radio Equipment was established by TELEC. The

study group specified the essential issues of SDR, and discussed effective methods to evaluate conformity to technicalregulations in SDRs. The biggest objective in SDR is to build an architecture that allows users to install software

exclusively using a combination of hardware and software that have passed the certification test. The study group also

proposed a checking system that uses a certification matrix and an array of registered data, by introducing new ideas

using tallies, as shown in Fig. 11, [3335].

The following outlines were given by the Federal Communications Commission (FCC) rule amendments for the

SDR radio regulations. In 1999, SDR was the focal topic of the FCC. In March 2000, the proceedings were officially

opened with a Notice of Inquiry (NOI) regarding SDR issued by the FCC. NOI distributed a 27-question survey to the

public. In Dec. 2000, the findings of NOI resulted in the FCC adopting a Notice of Proposed Rulemaking (NPRM)

regarding SDR that proposed rule changes to equipment certification for SDR. In September 2001, after a period of

public comment and replies, the FCC adopted its First Report and Order in the matter of Authorization and Use of

SDR. This was the first general SDR authorization in the world. It allowed equipment manufacturers to make

permissive changes in the frequency, power, and modulation parameters using software changes made to SDRs,

without having to file a new equipment authorization application. It also allows electronic labeling to reflect those

changes [18].

4. Conclusion

This paper describes trends in broadband wireless communication systems from today to beyond 3G and introduced

some recent achievements in cellular, WLAN, and FWA systems. Moreover, it gives a historical perspective of

software defined radios and describes the recent research and development activities, with a particular focus on

processor and security issues. Future wireless communication services will be provided using interconnections and

integrated with heterogeneous access technologies, including wired and indoor areas and provide access based on IP

networks. A concept of cognitive radio will be introduced to the future systems. Interconnections and seamless

handover technologies between various access systems are absolutely essential. Software defined radio is the key

technology for realizing these future systems and services.

Acknowledgments. The author would like to thank Dr. K. Hagimoto and Dr. M. Umehira for their valuable advice

and suggestions.

No. a c e

software

hardware

tally

S means application by SW manufacturer

H means application by HW manufacturer

means success in test

means failure in test

b d

Fig. 11. Example of method to assign tallies to hardware and software. (Check system using certification matrix) [34]



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