The channel capacity decreases with distance from the base station as a consequence of the the decreasing the signal to noise ratio in LTE systems. At the cell boundary, normally Bpsk modulation is used while the order of modulation may increase to 64 QAM or more near the center of the cell. This means a bandwidth efficiency increase of about five times from the cell boundary to the cell center.
So, the subscribers at the cell center are better served than those at the cell boundary. My question is how would the channel capacity be equalized among the the distance from the cell center?
Hi Prof.,
There are SNIR requirements for each MCS (Modulation and Coding Scheme) index. The SINR will be affected by transmission power, distance, interference and propagation model.
So, there is no definite answer on how to equalize the MCS with the distance unless you fix the other three factors and make MCS a function of distance.
I hope this helps.
You need to increase the SINR so that a higher modulation order can be supported (with a reasonably low error probability). Higher SINR is achieved by increasing the emitted signal power, using beamforming with multiple antennas at the base stations, and/or by decreasing the interference from other cells (e.g., by coordinated scheduling or beamforming).
I think, a solution of a optimization problem to equalize the capacity or the sum-rate of the system under the limited resources constraints will be suitable.
best regards
Dear Prof. Zekry
I think by using relays at the cell edge, you can equalise the channel capacity across the whole cell. The trick would be to position the relay in such a way such that the throughput of users served by the serving eNB would not be negatively affected by the relay access channels (due to the effectively higher noise levels at the vicinity of the serving eNB).
On the other hand, I think that increasing SINR would always give a higher throughput at the cell centre compared to the cell edge.
The powerful dynamic range and multiple superhetrodyning can maintain SIND,k in turn equalise the capacity
I would say that relays are good at providing range expansion, but less suited to equalize the throughput over the cell. This is because the two-hop transmission in relaying cuts the throughput in half. Hence, even if you can give the same SINR everywhere, you will get a data rate at the cell edge that is only 50% of the cell center.
Relaying using fixed infrastructure would be cheating in my opinion: this just moves the problem from "how can we serve those at the edges of a cell" to "how can we serve those farthest from a relay station". If the relaying would be done by the *other* mobile users, it would be a more fair solution.
I would put my money on Emil and Weisi: try to get as much power where you need it and as concentrated as possible. For example, the base station could transmit with lower power to those nearby and with higher power to those at the cell edges. Beamforming could also be used.
The question specifically mentions LTE. I am not an expert, but believe this is a multi-user OFDM system. So the previous objectives could be implemented in the digital domain, by putting more or less power on the carriers of far away and near-by users, performing digital beamforming, and possible also assigning more or less carriers to each user to even out their capacity.
Dear Colleagues,
Thank you much and happy new year for all of you.
From the conceptual point of view the channel capacity is limited by shanon theory
C= w log2 {1+S/N]
So the channel capacity C can be equalized by controlling the transmitted power such that it reaches the receiver with more or less the same value. May be one of the practical ways to achieve that is by beam forming. The second solution is to use MIMO for diversity.
One can decrease the interference and noise as the distance from the base station increases. This solution may not be practical since the interference naturally increases at the cell boundary.
Using relays can help in increasing the power at the regions far from the cell center.
One can increase w by frequency reuse or frequency clustering. Frequency reuse is achieved by space division using MIMO.
All these techniques are explained fully in LTE advanced standards.
Thank you
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2 Recommendations
Dejan Vujic
ENGCON
Shannon's capacity limit is more of theoretical value. I might misunderstood you but in essence you can't equalize channel capacity along the radius (length). Relaying is a trick that is based on adding a device along the path/radius. It is simpler version of adding new eNodeB and making smaller cells thus improving overall network capacity. For the required capacity you need to have proper C/I and RSS. If you would like to have in all points of a cell same throughput, you would need to keep it at the same coding scheme (same modulation) in every point of a cell which means reduction in cell radius to have required C/I and RSS. With mobile users and time variant channel it is always set in practice to target throughput that is necessary for the planned service and to guard C/I and RSS that would provide such service to end user. Without worrying if user could achieve more...
BR
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1 Recommendation
Made Yadnya
University of Mataram
Dear All
Mobile satiation moving cross the cell, I think is the problem because capacity channel destination must be have to use.
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