Discontinuous reception and transmission (DRX/DTX) strategies in long term evolution (LTE) for Voice-over-IP (VoIP) traffic under both full-dynamic and semi-persistent packet scheduling policies

Vinella, Dario ; Polignano, Michele

10. term

Elektronik og IT, Kandidatuddannelsen (Spec. Mobile Communication)

2009

123

Mobilsystemer som LTE har til formål at levere højere datahastigheder og lavere forsinkelser, hvilket åbner for nye mobile tjenester. Men når disse tjenester kører på batteridrevne enheder, opstår energiproblemer, fordi batterierne ikke har fulgt med softwarekravene. LTE reducerer strømforbruget blandt andet med afbrudt modtagelse (DRX) og afbrudt transmission (DTX): telefonen lytter ikke konstant på kontrolkanalerne og kan sætte radiomodemet i dvale, som vækkes på veldefinerede tidspunkter for at sende eller modtage data. Denne afhandling undersøger, hvordan Voice over IP (VoIP) kan bæres over LTE, så data leveres effektivt, passer til DRX/DTX, sparer strøm og ikke mærkbart forringer oplevelsen under opkald. Studiet modellerer en tovejssamtale og evaluerer to metoder til planlægning af radiokapacitet: semi-persistent planlægning (SPS) og dynamisk planlægning (DS). En enkel styremekanisme tilføjes SPS for at forbedre ydeevnen. Modellen omfatter også et modul til Channel Quality Indicator (CQI)-rapportering, linktilpasning (justering af transmissionsindstillinger efter radiobetingelser), styring af transmission og retransmission, en detaljeret DRX/DTX-ramme og en metode til at måle strømforbrug. Forskellige indstillinger for CQI-rapportering, linktilpasning og DRX/DTX (inklusive korte cykler) testes med én bruger og med mange brugere (250 ved cellekanten, hvor radiodækningen er svagere). Resultaterne viser, at DRX/DTX kombineret med SPS giver gode strømbesparelser, fordi timingen af talepakker, SPS og DRX/DTX typisk er synkroniseret. Forsinkelserne er acceptable i enkeltbrugerscenarier; i flerbrugerscenarier kan meget lange DRX/DTX-cykler medføre omkring 4% pakketab og forsinkelser, der strækker sig over hele taleperioden. DS udnytter kanalsporingen effektivt og vurderer hurtigt de nødvendige ressourcer, men den hyppigere signalering øger strømforbruget med cirka 33% i forhold til SPS. For både SPS og DS giver korte DRX/DTX-cykler ikke yderligere strømbesparelser for VoIP-trafik.

Mobile systems like LTE aim to deliver higher data rates and lower delays, enabling new mobile services. But running these services on battery-powered devices raises energy concerns because batteries have not kept up with software demands. One way LTE reduces power use is Discontinuous Reception (DRX) and Discontinuous Transmission (DTX): the phone does not listen to control channels all the time and can put its radio to sleep, waking at well-defined times to send or receive data. This thesis examines how to carry Voice over IP (VoIP) calls over LTE so that data is delivered efficiently, works with DRX/DTX, saves power, and does not noticeably affect call quality. The study models a two-way conversation and evaluates two radio resource scheduling methods: semi-persistent scheduling (SPS) and dynamic scheduling (DS). A simple control mechanism is added to SPS to improve its performance. The model also includes a Channel Quality Indicator (CQI) reporting module, link adaptation (adjusting transmission settings to radio conditions), managers for transmission and retransmission, a detailed DRX/DTX framework, and a way to measure power use. Different settings for CQI reporting, link adaptation, and DRX/DTX (including short cycles) are tested with one user and with many users (250 at the cell edge, where radio conditions are weaker). Results show that combining DRX/DTX with SPS yields good power savings because the timing of voice packets, SPS, and DRX/DTX are generally aligned. Delays are acceptable in single-user cases; in multi-user cases, very long DRX/DTX cycles can lead to about 4% packet loss and delays that span an entire speech burst. DS makes effective use of channel quality tracking and quickly estimates the needed resources, but its more frequent signaling increases power consumption by around 33% compared to SPS. For both SPS and DS, short DRX/DTX cycles do not provide extra power savings for VoIP traffic.

[This abstract was generated with the help of AI]

DRX ; DTX ; VoIP ; LTE ; SPS ; DS ; Semi-Persistent scheduling ; Dynamic Scheduling ; Power consumption ; Brady model

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