Issues with the D2D communication using PSC LTE D2D module

[aadesh shah]

Hello Zoraze,

Thanks for the reply, I hope you had a great vacation and I had mailed them before a week now but I haven't got any substantial response. Basically I need guidance for 3 problems which are stated as follows:

- When I Increase the traffic from 15 remote nodes to 20 remotes (the system has 80 relay nodes) the packet reception ratio reduces from 99.5 % to 80 % this is expected as I am assuming there will be a collision at the MAC layer. So I wanted to know how I can observe this collision such that it can help me improvise the system. Can you tell me the reason for this collision too? Plus is there a list of messages that are periodically communicated between the base station and the UE if I can increase the period then I can make more space on the channel as increasing the period of downlinkcqi doesn't help that much.

- When we use relaying the remote code forwards the packet to the relay node and the relay would decode the packet header and forward it to the destination. Now the whole process adds a delay. To reduce the delay I can reduce the processing time at the relay side. Can you tell me where this can be done? And another method would be to send the affirmative of the communication from the relay node itself to reduce the latency. Can you tell me how I can measure this? and even implement it?

- As I am using relaying for the factory environment the signals are pretty good I tried to reduce the power of the UEs dynamically but that doesn't help. And NS3 uses building blocking model only. So is there a way I can introduce blocking in the model such that there can me packet lost due to it?

 But I am relatively new to ns3 and cellular IoT too. But if you could answer these questions then it would be a great help for my graduation project. Any help would be useful.

Thank you and Regards,

Aadesh Shah

[Tom Henderson]

Hello Aadesh, I can try to provide some help, but because your questions
are not that specific and are asking about how to add new things to your
programs, you would have to post your code on a git repository somewhere
and show us exactly how to run your program and what additional
information or capability that you seek from that point.

- Tom

[aadesh shah]

Thank you for the reply Tom.

My apologies I will attach my code and ask specific questions in this post.

I will explain what I have implemented, I have factory model with 80 relay nodes and 20 remote nodes, the remote nodes start the relaying service as remote nodes according to their RSRP values. The relay nodes start their relaying service according to their RSRP values as relay nodes, if their RSRP value is less than the expected threshold then they stop relaying service (eliminating bad nodes). With this I have the following questions: 

1. When I increase the number of remote nodes and use sidelink for all the remote nodes than naturally I am dropping the packet reception rate from 100 % to 80%. Now I am assuming this is due to the collision on the sidelink. Am I correct? And collision can happen when the resource blocks are limited. So I wanted to know how I can see these values and where my packets are lost? are the due the collision of different kinds of messages (like cqidownlink, relay broadcasting etc) on the channel or are they due to the the same kind of the messages (messages from the application). Can you tell me how I can go in depth of this to know the loss of each packet and why?

2. In UE relaying network the implemented mechanism is decode and forward. And this adds processing time. Now in a simulation environment these values would be hardcoded. Can you tell me where I can find these values? I am asking this as I want to reduce the added latency due to decode and forward.

3. I am using the case for factories and the size of the factory is 50x50x6m with the base station positioned on the top. As the area is small its difficult to add a building blocking (as in ns3) I tried to reduce the power of the UEs but it was not that helpful. Can you tell me what can be done to add a realistic blocking model? (I am looking for ideas here)

I hope this time its more clear. Please let me know if I was not clear.

Thank you and Regards,

Aadesh Shah

[aadesh shah]

Hello Tom,

I found from the code it says the maximum destination for sidelink can be 16 does that mean if there are more than 16 active sidelink the packets would be lost? I am asking this because if I relay via 16 remote nodes simultaneously then I have a packet reception rate of 99.4 % but as soon as I increase the number of remote nodes to 17 the packet reception rate is reduced to 17. Can you tell me if there can be only 16 sidelinks active or more sidelinks are possible? if thats the case then can you tell me how? I tried to change the constraint parameters of #define MAXSL_DEST to 20, #define MAXSL_RXPOOL  to 20 in the lte-rrc-sap.h but I am still losing packets when I increase more than 16 nodes. Is this the right direction? And do I need to change something else to achieve more link?

Please let me know.

Thank you regards.

Aadesh Shah

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