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Introduction

Introduction. In IEEE 802.16m system requirement document (SRD), it was agreed that the higher spectral efficiency is required in 16m E-MBS at MBSFN deployment.

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Introduction

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  1. Introduction • In IEEE 802.16m system requirement document (SRD), it was agreed that the higher spectral efficiency is required in 16m E-MBS at MBSFN deployment. • In this contribution, we propose to apply a ‘group-wise scrambling’ technique into 16m E-MBS channel structure to improve MBS spectral efficiency. • There are two significant improvements in MBS spectral efficiency. • FDM between unicast and MBS resource becomes applicable without any additional pilot overhead. This makes power boosting of MBS data transmission possible using a margin of the BS transmit power of unicast data transmission. • Sub-carrier groups have the de-correlated channel response so that additional diversity gain is obtained.

  2. Conventional MBS Structure • Each BS transmit the same pilot and data signal. • MSs receive MBS signal with RF combining from each BS.

  3. Proposed Group-wise scrambling process • Split sub-carriers into several groups. • Each group contains at least one pilot symbol. • Scramble MBS data in each group with the same BS-specific code as pilot symbol. Cell-1 Cell-2 Cell-n Group-wise Scrambling Same as the BS-specific code used for pilot Cell-n

  4. Effects of proposed GS • Low correlation between sub-carrier groups • Additional diversity gain • Pilot symbols can be used by both unicast and MBS for channel estimation Possible cross-cast of MBS and unicast in sub-carrier level

  5. Channel estimation for GS • Pilot symbol only within sub-carrier group is used. • Sum of the weighted channel response is common in each sub-carrier group. • Channel estimation is employed within sub-carrier group. transmitted / received pilot signal transmitted / received MBS data signal

  6. Sub-carrier group partition • We define the sub-carrier groups as described below (assuming PUSC allocation). • Two pilot symbols within sub-carrier group is multiplied by the same scrambling code. • These pilot symbols in the same group can be used to improve the channel estimation performance.

  7. Advantage of GS (1) - MBS boosting - • Applying GS, unicast pilot can be used as MBS pilot in common so that sub-carrier based cross-cast becomes possible. • The margin for unicast transmission power can be used for MBS transmission as illustrated right side of figure.

  8. Advantage of GS (2) - Diversity effect - Table. Simulation condition Fig. MS location We assumed that MS is located at the BS-boundary with a geometry value of 95%. At that location, the r.m.s delay spread becomes almost the worst condition from the viewpoint of the delay spread. Diversity gain due to GS, relative to conventional MBS structure, is approximately 1.1dB at 1% BLER.

  9. Summary • We proposed to apply a group-wise scrambling technique into 16m E-MBS to improve MBS spectral efficiency. • We showed two significant improvements in MBS spectral efficiency obtained from this technique. • MBS Boosting • Additional diversity gain

  10. Proposed text in SDD 15. Support for Enhanced Multicast Broadcast Service 15.x E-MBS channel structure To improve MBS spectral efficiency, a group-wise scrambling is to be considered. The group-wise scrambling implies pre-coding method for the MBS data. The process includes: (1) All the MBS data sub-carriers are split into the sub-carrier groups with at least one pilot symbol. (2) All the MBS data symbols in each sub-carrier group are rotated by the same amount of phase as that of pilot symbol. Consequently, the relative phase differences from the pilot symbol to the MBS data symbols become the same. Since the signals within the sub-carrier group from each BS become the same, it is possible to realize the RF combining macro-diversity in the same manner as the BS-common pilot case. Fig. x. E-MBS channel structure with group-wise scrambling

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