Adaptive Modulation and Coding With Incremental Redundancy Hybrid ARQ in MIMO Systems: A Cross Layered Design.

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1 J Sofa Prya Darsn et al t Journal of Engneng Researc and Applcatons wwwjacom Vol 3, Issue 5, Sep-Oct 3, pp53-57 RESEARCH ARTICLE OPEN ACCESS Adaptve Modulaton and Codng Wt cremental Redundancy Hybrd ARQ n MIMO Systems: A Cross Layed Desgn J Sofa Prya Darsn*, Dr MV Subramanyam**, Dr K Soundararajan*** *(Department of ECE, RGMCET, Nandyal, Kurnool Dst, AP, da, 585) ** (Prncpal, SREC, Nandyal, Kurnool Dst, AP, da, 585) ** * (Prncpal, KITE, Ranga Reddy Dstrct AP, da, - 597) ABSTRACT Te present genaton wreless systems as sgnfcant growt n te demand for relable g-speed wreless communcaton lnks for multmeda applcatons lke voce, vdeo, e-mal, web browsng, etc Attanng gly relable lnks s a callengng task n wreless envronment MIMO explots space dmenson to mprove te system capacty, range, and relablty ts pap a cross layed approac wt Adaptve Modulaton and Codng (AMC) n te pyscal lay and cremental Redundancy Hybrd Automatc Retransmsson Request (IR-HARQ) n te data lnk lay s proposed for te fourt genaton MIMO systems Te proposed model mproves te transmsson rate and also relablty of te MIMO system Keywords - Adaptve Modulaton and Codng (AMC), cremental Redundancy Hybrd Automatc Repeat Request (IR-HARQ), Multple put Multple Output (MIMO) I INTRODUCTION or te present wreless communcaton systems, a novel drecton proposed to resolve te capacty requrements n te callengng rado envronment s te explotaton of MIMO systems MIMO systems found te way nto seval standards for future wreless communcaton systems, especally n Wreless Local Area Networks (WLAN) and cellular networks suc as IEEE 8, 86 and te 3 rd Group Partnsp Project (3GPP) [] Dvsty gan s aceved by Space-Tme Codng (STC) at te transmt sde, wc requres only smple lnear processng n te recev sde for decodng Cross lay arctecture s a desgn mecansm tat brngs toget te lays n ord to enance te system spectral effcency and trougput wle stll mantanng delay and pformance constrants Adaptve Modulaton and Codng (AMC) s used n te pyscal lay to mprove te system trougput by adaptng te transmsson rate to te tme varyng cannel condton at te transmtt Howev to aceve mamum relablty, t s requred to restrct te transmsson rates usng small constellatons To mtgate ts problem, Automatc Retransmsson Request (ARQ) s used n conjuncton wt AMC [][3] To meet te delay requrements truncated ARQ s used we te numb of retransmssons s lmted [4] A cross-lay desgn framework wt AMC and HARQ s proposed n [5] A new puncturng pattn for Rate-Compatble Low Densty Party Ceck codes (RC-LDPC) s used Te system proves to ave mproved spectral effcency To enance system pformance, cross layed desgn s proposed wwwjacom n [6] for QoS guaranteed traffc Te queung beavor nduced by bot te truncated ARQ protocol and te AMC sceme s analyzed wt an embedded Markov can Te ovall system trougput s mamzed und te specfed QoS constrants Howev, ter desgn ndeed cannot guarantee te same BER pformance at dffent transmsson pases of te ARQ protocol Hence cross layed desgn wt AMC and IR-HARQ s proposed we n dffent transmssons, dffent code words are transmtted tus mprovng te relablty of te system secton-, te MIMO system model s presented Secton-3 gves te system modelng usng IR-HARQ Effectve SNR and cannel estmaton s gven n secton-4te obtaned smulaton results are sown n secton 5 nally, concluson and future scope s gven n secton 6 II SYSTEM MODEL Te proposed model conssts of MIMO system wt T N numb of transmttng antennas and R N numb of recevng antennas as sown n g Convoluton Turbo codng (CTC) sceme s used to aceve dvsty n te proposed system nte state macne s mplemented to encode CTC long sequences of message bts usng sft regsts Te complety of te code s detmned by te memory of te encod defned by te numb of sft regsts If for eac set of k nformaton bts gven to te encod, n output bts are produced, ten te code rate s k/n Vtb algortm s used for te optmal decodng of a convolutonally coded sequence n AWGN modeled cannel 53 P a g e

2 J Sofa Prya Darsn et al t Journal of Engneng Researc and Applcatons wwwjacom Vol 3, Issue 5, Sep-Oct 3, pp53-57 Te dvsty ord for ts system s gven as: D T R N N () a retransmsson s nvoked Prevously transmtted data are tracked at te recev n ord to assocate te decodng, snce te cannel s known only at te recev Transmtt Recev I/p Convoluton Cod Modulator STBC Encod MIMO adng Cannels STBC Decod Vtb Decod O/P T N R N Cannel Estmator AMC and IR- HARQ controll eedback cannel Te cross lay approac connects pyscal lay and data lnk lay to enance te pformance of MIMO network Troug MIMO fadng cannels, te coded symbols are forwarded n te pyscal lay on a frame by frame fason subsequently usng Space Tme Block Codng (STBC) Varous modulaton and codng scemes (MCS) are used n te pyscal lay Te recev computes te Sgnal to Nose Rato (SNR) and sends back to te AMC controll If Y s te receved symbols matrx of ord R N ns and X s te transmtted symbols matrx of ord T N ns and N s te nose matrx of ord R N ns, te matrx elements are desgned as d complex crcular Gaussan random varables avng zo mean and unt varance ns stands for numb of symbols p antenna Te controll selects a sutable MCS for te next transmsson If ds s te data sequence, t s encoded nto z codewords we =,, z-tefore more tan one code words z may contan te part of nformaton n ds Te tecnque makes use of Convoluton Turbo Code (CTC) for encodng ds troug a rate-/3 mot code, wc s punctured to genate te z Dvse z may enclose common systematc or party bts of te mot code Te lengt of codewords (Le ) may not be equal [7] or te codeword z forwarded at evy transmsson, te receved sgnal s specfed as, Y, j, j, j N, j () He, block flat fadng s consded n wc cannel remans constant durng te transmsson of one symbol If te cannel s known only at te recev, te recev tres to decode te receved data If no ror detected or te decod corrects te rors ten te successful recepton s ndcated to te transmtt Ten, te system progresses on transmttng a new data sequence ds Upon a falure, g Block Dagram of te Proposed System III IR-HARQ te tme varyng wreless cannel redundancy of te system may be more tan te optmum value toug te cannel condton s good for non AMC system On te ot and, f te cannel s poor, more rors are expected to occur tan tose wc can be andled by te capablty of te ror-correctng code Consequently, too many retransmssons are requested, and te trougput falls down Tus, n ord to aceve optmum pformance, te rate of te ror-correctng code sould be matced to te prevalng cannel condtons [8][9] Hence IR-HARQ s proposed n te data lnk lay to reduce te numb of retransmssons and to meet te delay constrants for 4G systems At eac retransmsson, dffent code words z are forwarded n IR-HARQ Te modelng of IR-HARQ s sown n fgure-a Mamal Rato symbol Combnng () approac s used at te recev An optmal decson rule s used we te receved sgnals are lnearly combned troug dffent dvsty brances aft co-pasng and wegtng tem wt ter respectve cannel Te obtaned symbols are ten gven to a Mamum-Lkelood (ML) recev [] Wt, te receved symbols are collaborated as, Y n * Y n * n x x z (3) We, n * and n stands for te numb of transmssons To measure te Log-Lkelood Ratos (LLRs), te ML recev uses Y Y and, wc wll be transmtted to te decod so as to estmate te nformaton sequence ds wwwjacom 54 P a g e

3 J Sofa Prya Darsn et al t Journal of Engneng Researc and Applcatons wwwjacom Vol 3, Issue 5, Sep-Oct 3, pp53-57 A Y ds Encodng A Az- adng Nose Y Mamum Lkelood Decod ds IR-HARQ Control IR-HARQ Control Y z- gsystem Model for IR-HARQ If n transmssons are processed ten eac codeword wll be forwarded n tmes, we, =,,,z-, wt Z n Te measurement of te LLRs and n te decodng uses te sequences Y tat results from n combnng opatons If A s te set of symbols contanng bt,t can be represented as A a, a,, a n( ) (4) Its correspondng -combned symbols are gven as Y,Y,,Y n(b)- (5) IR-HARQ makes use of bt level combnng Te opaton of IR-HARQ s matematcally expressed as follows wwwjacom n( ) LLC BLC ( ) LLR n( ) L b Y, n( ) b Y Pr, Pr b Y, n( ) () () () () () Pr Y, n( ) () () () () () Pr Y, () exp Y () exp Y (6) (7) (8) (9) () sequences tat could equatons 9 and, () () ( ) are te sets of all possble symbol be forwarded on te cannel wen te value of β s equal to () IV SNR EVALUATION At te transmtt, te complex modulated symbols (R) are mapped by STBC encod nto T N ortogonal complex symbol sequences of lengt ns Tese mapped symbol sequences are forwarded concurrently by T N As a result, te codng rate (C R ) of a STBC s gven as R C R () ns Let AvgP be consded as te avage transmts pow for evy stream or antenna Before te computaton of mamum lkelood (ML), te receved symbol Y can be descrbed as p te effectve SISO cannel model for STBC as Y s N () We, te real and magnary part of te transmtted complex symbol s represented as s, s te squared matrx of robenus norm and te cannel coeffcent s gven as, = j (3), j Te SNR at te recev can be calculated as follows AvgP tp TNCR TNCR (4) He, tp s te total transmsson pow transmtted at antennas of T N or evy symbol duraton Te avage pseudo SNR ( ) s gven as, tp (5) Te probablty densty functon (PD) of can be descrbed wt te consdaton tat s te sum of D d random varables Tus, s descrbed as, D D T NCR T ( ) exp, ( ) NC (6) R P D He, () symbolzes te Gamma functon Assumng tat te computaton of te mnmum mean square ror (MMSE) n te cannel s carred 55 P a g e

4 Avage Rate(bps) J Sofa Prya Darsn et al t Journal of Engneng Researc and Applcatons wwwjacom Vol 3, Issue 5, Sep-Oct 3, pp53-57 out by te recev, te cannel coeffcent s descrbed as E wwwjacom (7) equaton (7), denotes appromaton of cannel matrx and E s te appromaton rorte proposed tecnque presumes tat and E are uncorrelated Elements n E are d, wc are te zo mean crculatory symmetrc complex Gaussan dstrbuted random varables wt varance of Te value of varance s gven as, E j E j (8) Te relatonsp between assessed SNR and nstantaneous SNR s defned as tp (9) Accordngly te PD of assessed SNR s gven as, D D P ( ) e, we () ( D) Te value of s, = TNCR tp () Te correlaton nvolves among j and assessed s j expressed as: E j j cl E j E j Equatons gven n (9) to () represents te qualty of cannel estmaton If l= =, ten and c V PERORMANCE EVALUATION Te pformance of te system s evaluated n tms of avage trougput and bt ror rate Te varous paramets used n te smulaton are tabulated n Table I MCS s based on te SNR values It s assumed tat te cannel state s known at te recev Te SNR s feedback to te MCS controll to select an optmal Modulaton and Code ratesnr mappng Modulaton and Codng Sceme (MCS) s sown n Table II Te smulaton results for te proposed system n tms of avage transmsson rate and bt ror rate are sown n fgure 3 and 4 resp Te proposed IR-HARQ wt AMC s compared wt te pformance of te system usng ARQ AMC It s evdent tat tat by cangng te MCS durng retransmssons, te trougput of te system s sgnfcantly mproved as sown n g3 Table I Smulaton Paramets Paramets Transmtts ( Nt ) Recevs (Nr) values Modulaton,4,6,64 Rate /,/3,/3 Numb of packets Codng tecnque Table II: MCS SNR Mappng SNR ( )db -5< < 5 5 < <5 5 < convolutonal Avage Transmsson Rate MCS Sceme M=, R=/ M=4, R=/ M=6, R=/3 M=64, R=/3 AMC and ARQ MIMO AMC and IR-HARQ MIMO SNR(dB) g3 Avage Transmsson Rate (AMC-ARQ Vs AMC-IR-HARQ) It s evdent from fgure-4 tat bt ror rate s apprecably reduced especally wen te cannel s good AMC and ARQ MIMO, BER decreases to - at 5 db weas for te AMC and IR-HARQ MIMO bt ror rate reduces to -3 Howev te ror rate s slgtly ncreased wen te cannel s vy poor 56 P a g e

5 Avage BER J Sofa Prya Darsn et al t Journal of Engneng Researc and Applcatons wwwjacom Vol 3, Issue 5, Sep-Oct 3, pp53-57 Avage BER AMC and ARQ MIMO AMC and IR-HARQ MIMO SNR(dB) g4 Avage BER (AMC-ARQ Vs AMC-IR- HARQ) Hence for te system wt AMC and IR- HARQ, te trougput s ncreased and te ror rate s sgnfcantly reduced wen te cannel s adequate VI CONCLUSION AND UTURE SCOPE MIMO usng AMC controll s used n most of te fourt genaton wreless communcaton systems Cross layed desgn usng AMC n te pyscal lay and IR-HARQ s used n te data lnk lay s used n te proposed system to ncrease te relablty of te system Te smulaton result sows tat te avage transmsson rate s mproved wt reduced bt ror rate Te pformance of te system s bett tan te estng system usng ARQ n tms of trougput tus makng te system more compactable for multmeda svces Te future scope of ts work can be empaszed on mprovng te pformance of te system at all cannel condtons Refences [] S-Y Len, K-C Cen, and Y Ln, Toward ubqutous massve accesses n 3GPP macne-to-macne communcatons, Communcatons Magazne, IEEE, vol 49, no 4, pp 66 74, Aprl [] GassaneAnba and Sona Assa, Cross- Lay Desgned Adaptve Modulaton Algortm wt Packet Combnng and Truncated ARQ ov MIMO Nakagam adng Cannels, IEEE Trans Wreless Communcaton, VOL, NO 4,pp6 to 3, APRIL [3] L Cao and P-Y Kam, On te pformance of packet ARQ scemes n Rayleg fadng: Te role of recev cannel state nformaton and ts accuracy, Vecular Tecnology, IEEE Transactons on, vol 6, no,pp 74 79, feb [4] JaumeRams and Gullememenas, Cross- Lay Desgn of Adaptve Multrate Wreless Networks Usng Truncated HARQ IEEE Transc on Vecular Tecnology, vol 6, no3,pp , MARCH [5] YulngZanga, DongfengYuana and Ceng- XangWang, Cross-lay desgn based on RC-LDPC codes n MIMO cannels wt estmaton rors, Elsev, tnatonal Journal of Electronc Communcaton, (AEÜ), pp , 8 [6] Xn Wang, Qngwen Lu and Georgos B Gannaks, Analyzng and Optmzng Adaptve Modulaton Codng Jontly Wt ARQ for QoS-Guaranteed Traffc, IEEE Transactons on Vecular Tecnology, Vol- 56, No-, Marc, 7 [7] D Wu, and S C, Cross-lay combnaton of ybrd ARQ and adaptve modulaton and codng for QoS provsonng n wreless data networks, n Proc 3rd t l Conf Qualty of Svce n Hetogeneous Wred/Wreless Networks (QSne), Watloo, August 6 [8] S Aïssa and G Anba, BER analyss of M- QAM wt packet combnng ov spacetme block coded MIMO fadng cannels," IEEE Trans Wreless Commun, vol 7, no 3, pp , Mar 8 [9] DmtrsToumpakars, Jungwon Lee, Adna Matace, and Hu-Lng Lou, Pformance of MIMO HARQ Und Recev Complety Constrants, IEEE Global Telecommuncatons Confence, (GLOBECOM 8), pp--5, 8 [] Jan Q, and Sona Assa, Cross-lay desgn for multus MIMO beam formng systems wt feedback constrants," IEEE Trans Ve Tecnol, vol 58, no 7, pp , Sep 9 wwwjacom 57 P a g e