HARQ PROCESS IN LTE EPUB DOWNLOAD
FDD-LTE uses 8 HARQ Parallel Process having unique process ID 0, 1, 2 7 (3 bits reserve for HARQ Process ID in DCI Messages). Jump to HARQ Process - A little bit different mode of HARQ process is used depending on whether it is for FDD or TDD and whether it is for Uplink and Downlink. But I will talk only about FDD case. In FDD, we are using 8 HARQ process. a) it can use the 8 HARQ processes in any order (Asynchronous Process). Agenda item: Source: LG Electronics. Title: HARQ process mapping across aggregated component carriers. Document for: Discussion.
|Published:||4 January 2014|
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We consider such a mechanism as efficient when it allow data communication in a link meet quality requirements that the service demands QoS.
Voice for example, is a service where retransmission does not apply. If a piece of information is lost, and is retransmitted, the conversation becomes intelligible.
Harq Process - Ask the Expert - Ask the Expert! - LTE University
On the other hand, data services practically rely harq process in lte retransmission, since most have - or allows - a certain tolerance to delays — some more, some less. With the exception only for 'Real Time' services.
But it is also important to take into account that the greater the number of needed retransmissions, lower the data transmission rate that is effectively reached: If the information have to be retransmitted several times, it will take long for the receiver to obtain the complete - final - information.
Harq process in lte Till now we talked in a generic way about data retransmissions, error checking and correction.
Let's now see some real and practical schemes. In ARQ, when we have a 'bad' package, the system simply discards it, and asks for a retransmission of the same package.
And for this, it sends a feedback message to the transmitter. These feedback messages are messages that the receiver uses to inform whether the transmission was successful or not: These messages are transmitted from the receiver to the transmitter, and respectively informs a good ACK harq process in lte bad NACK reception of the previous packages.
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If in the new retransmission the packet keep arriving with errors, the system requests a new retransmission still for this same package. That is, sends another 'NACK' message. The data packets that are not properly decoded are discarded.
The data packets or retransmissions are separately decoded. That is, every time a packet that arrives is bad, it is discarded, and it is requested that this same package be retransmitted.
But see that if there were no retransmissions, the performance of harq process in lte data flow would be much better. In the example below, compared with the previous, we harq process in lte more information - 3 times in the same time interval.
Unfortunately we don't have much to do about the link conditions.
What is Retransmission, ARQ and HARQ? - telecomHall
Or better, we are able to improve the links performance, for example with configuration parameters optimization, but we'll always be subject to face adverse conditions.
In this case, harq process in lte only way out is to try to minimize retransmissions. And that's where arise other techniques or more 'enhanced' schemes for retransmission.
The main one is HARQ.
LTE in WIRELESS: HARQ in LTE
With the 'Soft Combining' data packets that are not properly decoded are not discarded anymore. The received signal is stored in a 'buffer', and will be combined with next retransmission.
That is, two or more packets received, each one with insufficient SNR to allow individual decoding can be combined in such a way that the total signal can be decoded! The following image explains this procedure.