WiMAX Based 60 GHz Millimeter-Wave Communication for Intelligent Transport System Applications

Transcription

1 Internationa Journa of Wireess & Mobie Networks (IJWMN) Vo. 3, No. 2, Apri 211 WiMAX Based 6 GHz Miimeter-Wave Communication for Inteigent Transport System Appications 1 Bera Rabindranath, 2 Sarkar Subir Kumar, 3 Sharma Bikash, 4 Sur Samarendra Nath, 5 Bhaskar Debasish & 6 Bera Soumyasree 1,3,4,5,6 Sikkim Manipa Institute of Technoogy, Sikkim Manipa University, Majitar, Rangpo, East Sikkim, : 2. Jadavpur University, Kokata {rbera5,samar.sur,debasishbhaskar,soumyasree.bera}@gmai.com Abstract With the successfu wordwide depoyment of 3rd generation mobie communication, security aspects are ensured party. Researchers are now ooking for 4G mobie for its depoyment with high data rate, enhanced security and reiabiity so that word shoud ook for CALM, Continuous Air interface for Long and Medium range communication. This CALM wi be a reiabe high data rate secured mobie communication to be depoyed for car to car communication (C2C) for safety appication. This paper reviewed the WiMAX,& 6 GHz RF carrier for C2C. The system is tested at SMIT aboratory with mutimedia transmission and reception. With proper depoyment of this 6 GHz system on vehices, the existing commercia products for 82.11P wi be required to be repaced or updated soon. Key words: C2C, CALM, WiMAX, WiFi, VSG, RTSA. 1 Introduction Safety and security are very important in car-to-car communication. It is even more important when wireess systems are used because it is generay perceived that wireess systems are easier to attack than wireine systems. In search of best, secured and reiabe communication technoogy towards next generation e-car safety appication, IEEE 82.16, an emerging wireess technoogy for depoying broadband wireess metropoitan area network (WMAN), is one the most promising wireess technoogy for the next-generation ubiquitous network. Though IEEE82.11P WiFi based products are commerciay avaiabe for same functionaity. But, disadvantages incurred in the Wi-Fi security have been addressed into the IEEE standard and aso fexibiity parameters are aso addressed in WiMAX. WiMAX is designed to deiver next-generation, high-speed mobie voice and data services and wireess ast-mie backhau connections [1] The University of Texas at Austin. IEEE 82.16e (Mobie WiMax) deas with the Data Link Layer security. The Data-Link Layer authentication and authorization makes sure that the network is ony accessed by permitted users whie the encryption ensures privacy and protects traffic data from hacking or spying by unauthorized users. The WiMAX 82.16e provides number of advanced security protections incuding: strong traffic encryption, mutua device/user authentication, fexibe key management protoco, contro/ management message DOI : /ijwmn

2 Internationa Journa of Wireess & Mobie Networks (IJWMN) Vo. 3, No. 2, Apri 211 protection, and security protoco optimizations for fast handovers when users switch between different networks. Fig.1 shows a WiMAX architectura components Fig. 1. WiMAX architectura components [2]. Commercia products of vehicuar networks exists viz. DENSO's Wireess Safety Unit (WSU), Hitachi-Renesas. DENSO s Wireess Safety Unit (WSU) is the foow up deveopment to DENSO s first generation 82.11p communication modue, the Wave Radio Modue (WRM). It is specificay designed for automotive environments (temperatures, shock, vibration) and has its primary focus on safety reated appications. [4] During norma driving, the equipped vehices anonymousy share reevant information such as position, speed and heading. In a C2C environment message authorization is vita. The possibiity to certify attributes and bind those to certain vehices is particuary important for pubic safety. [5] Fig. 2. Shows a possibe attack in a typica Car2Car environment. Assuming no security, his attacker coud generate vaid messages for and consequenty disturb the whoe transportation system. Whie unicensed spectrum around 2.5 GHz and 5 GHz is aso avaiabe internationay, the amount of avaiabe 6G bandwidth is much higher than that around 2.5GHz and 5GHz [3]. 215

3 Internationa Journa of Wireess & Mobie Networks (IJWMN) Vo. 3, No. 2, Apri 211 Unicensed spectrum surrounding the 6 GHz carrier frequency has the abiity to accommodate high-throughput wireess communications. It is highy directive and can be used for ong and directed ink. 6GHz system enjoys the size reduction and cost reduction advantages. Additionay, due to avaiabiity of 5GHz bandwidth the data-rate for communication is more interesting. Many commercia products have been deveoped facing these chaenges. Thus,exporing the WiMAX 82.16e for its security, reiabiity and high throughput features, exporing 6 GHz miimeter wave as carrier for its size and cost reduction, wide bandwidth and highest throughput, the Car2Car communication system is required to be deveoped for the next generation Car for safety appications. The deveopment of 6 GHz C2C communication system comprised of two step procedure discussed beow. The MATLAB/SIMULINK is used for the design verification and simuation at the 1 st stage. The fina simuation resut in the form of *.md fie is ported to the ARB unit of one R&S VSG for the reaization of the base band hardware. The transmit IF at 1 GHz and transmit RF at 6 GHz are reaized through RF bock of R&S VSG and separate 6 GHz transmit modue respectivey as shown in figure 8 and 9 respectivey. The signa reception is deveoped using 6 GHz RF front end, RF Tuner and RTSA ( Tektronix rea Time spectrum anayzer). in Laptop, Data is retrieved at the Laptop using data acquisition and digita signa processing. The above system deveopment efforts are discussed beow. Section 2 reates the mathematica modeing of sub-carrier generation. Section 3 wi discuss a about WiMAX simuation at the base band eve. The successfu deveopment of section 3 wi produce one *.md fie which is ported to the VSG for base band hardware reaization. Section 4 wi discuss the efforts pertaining to hardware deveopment. 2 Mathematica modeing of Sub-carrier generation The seria data input is a sequence of sampes occurring at interva T s. At the transmitter as shown in Fig 3, the high rate seria input data is converted to coumn data which is of ower rate. The ow-rate coumn data consists of M ow-rate parae streams in order to increase the symbo duration to T=MT s. The ow-rate streams, represented by the symbos b m [k], m=, 1, 2,..., M-1, and k=1, 2, 3..., where each stream is moduated onto different sub-carriers. The orthogona reationship between any two of the sub-carriers in a set is maintained to avoid the Inter Channe Interference [8]. Then the parae streams are mutipexed and a Cycic Prefix is inserted to eiminate the effect of Inter Symbo Interference. So, we obtain the transmitted k th symbo as beow. M 1 m= y(t) = b where, G + kt t (k + 1) T (1) j2πmt / T m [k]e, G is the ength of the Guard Interva and at the m th stream of data the kth symbo is coming out as b m [k]. Now this y(t) wi pass through the channe which can be modeed as the frequency seective fading channe and it wi aso have the mutipaths. This type of channe mode can be reaized if we consider the tapped-deay ine with time-varying coefficients with a fixed tap spacing. The foowing is the mathematica reaization of such type of channe [8]. 216

4 Internationa Journa of Wireess & Mobie Networks (IJWMN) Vo. 3, No. 2, Apri 211 χ = h (t, τ) = h (t) δ( τ τ ) (2) h (t) and τ are the compex ampitude and deay of the th path, respectivey. χ+1 is the tota number of taps. τχ is the maximum mutipath deay spread. For OFDM symboization, the ength of G shoud be greater than τ χ. The expectation vaue of h (t) is the determining factor to get the foowing correation function. As h (t) is random in nature, it is modeed as the Wide-Sense Stationary Uncorreated Scattering process. * 2 φh ( t) = E[h (t)h (t t)] = σ φ t ( t) (3) The received signa r(t) in the kth symbo can be represented as χ h(t, τ)y(t τ) = = r (t) = h (t)y(t τ ) + n(t) (4) n(t) is the background noise. For practica impementation, moduation and demoduation can be achieved by Inverse Fast Fourier Transform (IFFT) and Fast Fourier Transform (FFT), respectivey. Channe estimation is appied to obtain the estimates of channe fading in each sub-carrier such that coherent detection is achieved. Let q be the sub-carrier index at the output of the OFDM demoduator in a WiMAX system and s k,q is the output for the q th sub-carrier in the k th symbo interva. Now, et us assume that the channe impuse response is quasi-static during the k th symbo interva so that h( t) h( kt) for kt t < ( k + 1) T, the Inter Carrier Interference can be negected compared to the background noise n(t). Thus the k th sub-carrier output,,q {, 1, 2,..., M 1}, from the demoduator can be expressed as s k, q s k,q 1 = T 1 = T = c (k+ 1)T k,q kt χ = H k,q χ = h (kt) + v h (kt) M 1 m m= k,q b M 1 m m= [k]e b [k]e j2πm τ )/T j2πm(t τ )/T (k+ 1)T j2π(m q)t / T kt e + n(t) e j2πqt/t 1 dt+ T (k+ 1)T kt n(t)e j2πqt/ T dt (5) where, χ (k+ 1)T j2πqτ / T 1 j2π / T c = = = qt k,q bq[k], Hk,q h (kt)e and vk,q n(t)e dt (6) = T kt If the channe fading is characterized by H k,q were known, then coherent detection and optimum diversity combining woud be achievabe at the receiver. H k,q is time varying and usuay unknown. Hence, for the accurate estimation of the channe fading parameters, H k,q is to be evauated for a given s i,q, i k and q =, 1,..., M

5 Internationa Journa of Wireess & Mobie Networks (IJWMN) Vo. 3, No. 2, Apri WiMax Simuation at baseband eve The fu WiMAX simuation is shown in the Fig 3. Fig. 3. The Simuink mode of WiMAX transmitter and receiver. The descriptions of some important bocks are as foows: (1) Data generator [MAC PDU] bock under 'data' bock: The standard is designed with the network and communication security keeping in considerations. Over the wireess ink the robust security aspects are to be considered as the most important to contro the confidentiaity during data communication. In standards, the security keys and encryption techniques are invoved as shown in the Fig. 4. It has the simiarity in concepts of adopting the security parameters as of IPsec. After the authorization from Security Association, the X.59 certificate, consists of an authorization key (AK), a key encryption key (KEK), and a hash message authentication code (HMAC) key, which are used for authorization, authentication, and key management [6] Here in the foowing mode, we have 1 bocks utiized for message authentication and security management. From the top to bottom, those bocks are: (i) HT: Header Type, (ii) EC: Encryption Contro, (iii) Type: Payoad Type, (iv) RSV: Reserved, (v) CI: CRC Identifier, (vi) EKS: Encryption Key Sequence, (vii) RSV: Reserved, (viii) LEN: Length of Packet, (ix) CID: Connection Identifier and (x) HCS: Header Check Sequence. In terms of message authentication, there are some important shortcomings in IEEE standard impemented at the MAC Layer. To avoid the serious threats arise from its authentication schemes, the WiMAX invoves a two-way sequentia transactions for controing, authorization and authentication. During the basic and primary connection, MAC management messages are sent in pain text format which is not a robust type of authentication and so can be easiy hijacked over the Air and this can be done by the attacker once again. So, as per the X.59 Certificate, the Pubic Key Infrastructure (PKI) defines a vaid connection path to identify a genuine Security Systems. It uses RSA Encryption with SHA1 hashing. The certificate, as pre-configured by the specific manufacturer and embedded within the system 218

6 Internationa Journa of Wireess & Mobie Networks (IJWMN) Vo. 3, No. 2, Apri 211 must be kept secret so that it can not be stoen by other users/vendors. A Security System that is certificated by a particuar manufacturer is impemented in a Base Station (BS) and the particuar BS can not know the interna standards priory. Fig. 4. The MAC PDU generator incuding header scheme and payoad Since, mutua authentication verifies the genuineness of a BS, it shoud be present in any wireess communication as it is virtuay open to a. Extensibe Authentication Protoco (EAP) is mosty utiized in any WiMAX Base Stations as to protect IEEE / WiMAX against masquerading parties. The spectrum of the base band just after the Mac PDU packing is shown in Fig.5. (2) The PN spreading bock Fig. 5. Base band spectrum The incoming signa is XOR'd with the bit pattern generated by a PN Sequence Generator. This is further zero padded to increase the frame size to The Chip sampe time is 1/1 S, so the chip rate is 1 KHz. The spectrum after spreading ooks ike as shown in the figure 6 beow: The bit pattern generated after this is fed into a bit to integer converter and then to a QPSK moduator. 219

7 Internationa Journa of Wireess & Mobie Networks (IJWMN) Vo. 3, No. 2, Apri 211 Fig. 6. Spectrum after spreading (3) The Sub carrier Generation and packing sub system: Fig. 7. Input packing before IFFT transformation and cycic prefixing After the QPSK moduation, piot is inserted which heps in channe estimation. Here input stream is broken down into 1 different data pipes and piots inserted in between them according to the above figure. A the rows of the resuting data are combined before feeding it to the IFFT bock for sub carrier generation in time domain and then cycic prefixing to add guard time. The fina Tx bocks ooks ike as depicted in Fig.7. 4 Hardware Impementation of the 6 GHz System 4.1 Description of Transmitter Section The prototype mode of the 6 GHz transmitter is shown in Fig.8 and its bock schematic diagram is shown in Fig.9.The Tx section consists of severa parts as shown in Fig.9. The PC is used to programme the VSG using Matab/ Simuink for the generation of two orthogona basis functions [9]. In the base band section we programmed the ARB section of the VSG to generate the base band WiMAX signa and it is then up converted to IF eve of 1 GHz and fed to the 6 GHz varactor tuned Gunn osciator. The basic bock diagram is shown in the Fig.9. The Gunn osciator is foowed by 6 GHz attenuator and frequency meter for the contro and frequency measurement of 6 GHz transmitted signa respectivey [7]. The 2 feet paraboic disc antenna is connected at the output for radiation of 6 GHz signa 22

8 Internationa Journa of Wireess & Mobie Networks (IJWMN) Vo. 3, No. 2, Apri 211 Fig. 8. The 6 GHz Transmitter 4.2 Description of Receiver Section Fig. 9. Bock diagram of the WiMAX Transmitter The prototype mode of the 6 GHz receiver is shown in Fig.1. The bock schematic diagram is shown in Fig.11 where the receiver consists of a front end, which receives signa through a horn antenna. The received signa then down converted to IF eve (1 GHz) using 61GHz Gunn osciator. This signa is further ampified by two IF ampifiers and is fed to input of the DVB sateite receiver tuner. The I-Q signa from the receiver tuner is connected to the RTSA as shown in Fig.11. We store the received I-Q data in RTSA for further anaysis, as shown in Fig.14. Fig. 1. The 6 GHz Received RF Front End Fig. 11. Bock diagram of the 6 GHz WiMAX receiver 221

9 Internationa Journa of Wireess & Mobie Networks (IJWMN) Vo. 3, No. 2, Apri 211 The Rx spectrum at IF eve is shown in Fig.13. Fig. 12. The fina transmit spectrum Fig. 13. Received spectrum with bandwidth is 1.75 MHz The Received In-Phase and Quadrature-Phase Signas in Rea Time Spectrum Anayzer is shown in figure 14. Fig. 14. Received I, Q Signas in RTSA 222

10 Internationa Journa of Wireess & Mobie Networks (IJWMN) Vo. 3, No. 2, Apri Concusion Fig. 15. Received WiMAX Sub-Carriers in RTSA Lots of efforts are imparted for the deveopment of the 6 GHz C2C ink. The system is tested at SMIT aboratory with mutimedia transmission and reception. Technica expertise are deveoped towards Simuink programming, methods of poring to VSG, IF and miimeter wave hardware, RTSA use, Data Acquisition and DSP. The system is operationa at SMIT aboratory but yet to be tested after mounting on the vehices. This successfu deveopment encourages the active groups at the aboratory. With proper depoyment of this 6 GHz system on vehices, the existing commercia products for 82.11P wi be required to be repaced or updated soon and we ook forward for the improved society with inteigent vehices. References 1. 6GHz Wireess Communications: Emerging Requirements and Design Recommendations Robert C. Danies and Robert W. Heath, Jr. 2. WiMAX Security for Rea-Word Network Service Provider Depoyments 3. White paper Airspan Mobie WiMax Security 4. DENSO s WSU Unit Car-to-Car Communication Consortium 5. C2C-CC Security Baseines, Car2car communication consortium IEEE 82.16/WiMax Security Hyung-Joon Kim Dept. of Eectrica and Computer Engineering Stevens Institute of Technoogy, Hoboken, New Jersey. 7. Miimeter-Wave Radar Technoogy for Automotive Appication by Shinichi Honma and Naohisa Uehara 8. Channe Aocation and Routing in Wireess Mesh Networks: A survey and quaitative comparison between schemes F. Kabbi, S. Ghannay, and F. Fiai Internationa Journa of Wireess & Mobie Networks (IJWMN), Vo.2, No.1, February Muti-Standard Programmabe Baseband Moduator For Next Generation Wireess Communication Indrani Hatai and Indrajit Chakrabarti, Internationa Journa of Computer Networks & Communications (IJCNC), Vo.2, No.4, Juy