WARP Project Forums - Wireless Open-Access Research Platform

You are not logged in.

#1 2018-Apr-16 07:26:57

fc
Member
Registered: 2016-Oct-14
Posts: 15

packet

Hi, I send a packet which is made up with [preamble payload]. First, I acquire the phase1 of packet in time domain. Then, I quickly send another packet, and extract the phase2 of the packet. In theory, the phase1 should be equal to phase2. However, the phase1 is unequal to phase2. Could you tell me the reason of the problem, and how to deal with it.

Thanks  a lot

Last edited by fc (2018-Apr-16 07:27:34)

Offline

 

#2 2018-Apr-16 09:31:02

murphpo
Administrator
From: Mango Communications
Registered: 2006-Jul-03
Posts: 4924

Re: packet

In theory, the phase1 should be equal to phase2.

This is only true if:
-Tx and Rx nodes are perfectly synchronized (zero carrier frequency offset, zero sampling frequency offset); and
-The propagation channel is perfectly static

In all other cases you will observe phase variations between Tx and Rx baseband signals.

Offline

 

#3 2018-Apr-18 02:05:08

fc
Member
Registered: 2016-Oct-14
Posts: 15

Re: packet

yes,what you said is true. So now i want to know how to eliminate the phase offset, could you provide some  methods for me to solve it. Another, I want to know the range of variations of the observed phased in most situation.

Thanks

Offline

 

#4 2018-Apr-18 10:33:19

chunter
Administrator
From: Mango Communications
Registered: 2006-Aug-24
Posts: 1171

Re: packet

It depends. You'll need to study this problem with something like WARPLab to determine how phases drift. I wouldn't expect much coherence in channel phases from packet to packet. If the Tx and Rx nodes are independently clocked and the time between the two transmissions is perfectly deterministic, the difference in channel phases will be the joint effect of two things. (1) Carrier Frequency Offset (i.e. frequency offset between the kits over the duration of the gap in time between the two transmissions) and (2) Fading of the wireless channel (which depends on all sorts of things like velocity of reflectors in the environment)

Offline

 

Board footer