Hi Anand,

Broadcasting in general means sending a message (or signal) to all receivers. You are right that the superimposed signal is in fact broadcast (all receivers receive this superimposed signal). However, the goal of each receiver is to extract the specific signal intended for it. Or in other words, downlink NOMA is still used by the base station to serve multiple receivers with individual signals.

Also, if you think about LTE for example, the situation is similar: OFDMA is used to multiplex the respective signals intended for multiple users (downlink). The difference is that while OFDMA uses the frequency and time domain for multiple access, NOMA uses the power domain instead. See also this question: https://www.researchgate.net/post/What_is_Non_Orthogonal_Multiple_Access_NOMA_for_wireless_communications

Best regards,

Alex

As indicated by the NOMA terminology, it is a multiple access technique. However, NOMA is breaking the orthogonality that is achieved by the traditional orthogonal multiple access (OMA) approaches. For example, in the OFDMA and TDMA based techniques, the resources are allocated to the user terminals in an orthogonal way and hence, there is no intra cell interference. However, the OMA based approaches suffer from inefficient utilization of the spectral resources. Therefore, there is a trade-off between NOMA and OMA based techniques.

Best

Hi, Anand Jee

As far as I understand, NOMA is about overloading the frequency or time resource sharing, i.e., sharing these resources among more users by overlapping the frequency bands and time slots. In this scheme, despite the overlapping frequency bands or time slots, data symbols intended for each user is still transmitted through its own frequency band or time slot.The broadcasting scheme on the other hand means transmitting one data symbol through one frequency band or time slot which is common among all users, i.e., full overlapping or transmitting the same data symbol for all users in different frequency or time resources. In case of NOMA, each user receives its own data symbol plus traces of data symbols intended for other users while in broadcasting scheme all users receive the same data symbol. Obviously, in NOMA scheme if the same data symbol is transmitted through overlapping frequency bands or time resources of different users then that single data symbol is broadcasted to those users.

Hello Marwah Abdulrazzaq Naser

Thank you for your reply. Still, it is not clear to me that why the name is Downlink NOMA. As per the name, it is a Multiple access technique but it broadcast the superimposed signal in the downlink phase. Multiple access allows multiple users to share the resource in the uplink phase while broadcasting allows the base station to serve multiple users in the downlink phase. So, both these phenomena can not be merged. Do correct me if I am wrong

I think the difference is that for broadcasting, we broadcast the same information. Whereas for down link NOMA, we send different information to different people. That's why its multiple access

Hi, Arooj M Siddiqui

The base station transmits a superimposed signal and all receivers receive the same signal (superimposed signal ), after applying SIC they extract their own signal. So in my opinion downlink, NOMA BS does not send different information to different users but they extract according to their requirement. Correct me if I am wrong.

thats bit tricky basically NOMA uses the power domain so the requirement and power change can not put it under the category of broadcasting

Thank you for the information.

NOMA is a novel and promising multiplexing scheme for future radio access. Please read the following paper for more details:

https://pdfs.semanticscholar.org/1477/8c987b13e776e69bdf63168502837a6a8c93.pdf

NOMA is a multiple access technique because same channel is shared non-orthogonally by multiple users based on power-domain.

Dear Md Fazlul Kader, in downlink NOMA the channel from the base station to each user differs.

Here is Concept , standards and Throughput analysis for power domain in NOMA system in 5G. Please read the following paper for more details:

https://www.ijrte.org/wp-content/uploads/papers/v8i3S/C10191083S19.pdf

Thank you Sam Mhd Mhd