LTE - RTT over distance for different number of UEs

[David T]

Dear All,

I am experimenting on a simple LTE scenario to judge the effect of RTT over distance by increasing the number of UEs ( moving with ConstantVelocityMobilityModel). However, for a particular number of UEs (say 30) I couldn't see any difference on RTT as the distance increased from 500 - 9500 meters. My expectation was RTT increases over distance (due to signal attenuation) and the number of UEs (due to congestion/interference). My question is, on which attributes should I play around to get desired output? Thank you!

[pdbarnes]

First, over that short a distance the change in propagation delay, latency, is still very small, 3.3 microseconds over 1000 m.

Second, IIUC LTE has the UEs compensate by starting their transmissions early, so the signal arrives at the eNodeB at the scheduled time. In other words, the guard time is entirely at the UR, so there is no (or extremely little) jitter at the eNodeB.

Peter

[David T]

Thank you peter.
But consider the following phrase that I have taken from ns-3-users group discussions

1. "the coverage range is defined by the a set of transmissions parameters, the main ones are represented by: transmission power, noise, antenna model, pathloss model and interference."
2. "To influence the coverage of an eNodeB, you can try to configure the antenna model and/or the Tx power used by the eNodeB. The eNodeB antenna model can be configured through LteHelper functions (SetEnbAntennaModelType and SetEnbAntennaModelAttribute), while the Tx power can be configured by changing the value of attribute TxPower in LteEnbPhy"
3. " The Nakagami-m only gives you the FastFading effect which simply vary the RxPower according to a Nakagami distribution. In order to have also the effect of distance, then you add the Three Log Distance or any other model you want"

We can sum from those facts coverage range depends on many parameters. From this can't we conclude that propagation delay of the farthest distance is higher than the closest places to eNodeB?

[Konstantinos]

Hi,

No, you can not make such conclusions. You can conclude that nodes further away may have more dropped packets due to the path loss, but the propagation delay is as Peter said 3,3microsec per km (speed of light). You may have more retransmissions which would increase overall latency.