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Introduction

Introduction. Objective Improve the efficiency for transmitting small packets to multiple users Support for low data rate/real-time applications such as Voice over IP Multi User Frame Description

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Introduction

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  1. Introduction • Objective • Improve the efficiency for transmitting small packets to multiple users • Support for low data rate/real-time applications such as Voice over IP • Multi User Frame Description • Modified preamble structure for the encoder packets allows the partially filled encoder packets to one multiplex other user’s data if available and/or transmit at a lower data rate to improve the FER • Multiplex up to 4 users in one frame for transmitting high data rates • Reduce the maximum HDR physical layer packet size from 512 bytes to 128 bytes

  2. HDR Preamble Structures HDR Frame Structure • For data rate >= 1.2288 kbps, the traffic payload for the high data rate encoder packets can be shared among several users • Each user may receive one or more FTC packets • In this case, the preamble has ‘head room’ to support more than one AT ID

  3. Modified Preamble Structure • For transmission data rate < 1.2288 Mbps, maintain the HDR preamble structure • For transmission data rate >= 1.2288 Mbps, we propose change the preamble length to 128 chips, and divide it into the several fields Preamble Duration Modulation Phase I- Branch Null I1 I2 Q- Branch EDRI Q1 Q2 64 chips 32 chips 32 chips

  4. Explicit Data Rate Indicator (EDRI) • EDRI is only set when the transmission rate is 1.2288 Mbps or higher. For lower data rate, HDR preamble (MAC identifier on I channel) will be used • EDRI is (8,4,4) bi-orthogonal coded and block repeated 8 times • EDRI specifies one of the following rate: 1.2288 Mbps, 1.8432 Mbps, 2.4576 Mbps • If a user requests DRC >= 1.2288 Mbps, and EDRI is set, then the user have to check the MAC Identifiers to see if the packet is for him

  5. MAC Identifiers • I1,I2,Q1,Q2 are 32-ary Walsh coded MAC Identifiers

  6. Multi-User Frames forData Rates >=1.2288Mbps • Assign FTC Packets destined to one or more ATs to an Encoder Packet such that the data rate requested by each AT is > or = the data rate of the Encoder Packet. • Note: In the event FTC packets are only available for a single AT, then transmit an Encoder Packet at the lowest data rate capable of transporting the available FTC packets. This maintains throughput while improving the Encoder Packet error rate. • For example: Transmission is scheduled for an AT. The data rate requested by the AT is 2457.6 kbps and the queue for this AT contains 2 FTC Packets. No other FTC packets are available for multiplexing. Then the 2 FTC Packets are transmitted in an Encoder Packet at 1228.8 kbps.

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