NR is a new air interface that is not backward compatible with LTE, LTE⁃Advanced or LTE⁃Advanced⁃pro.

NR networks can be independently deployed without relying on any 2G, 3G or 4G networks. This means that NR should have a complete set of RAN functionalities to be able to work alone.

Similar to previous generations of cellular networks, NR should have basic frame structure, numerology, initial access procedures, and scheduling for operation.

In some sense, these basic components for 5G NR system may inherit lots of design of previous generations, in particular 4G standards. It is apparent that multiple access schemes for NR would be at least based on orthogonal frequency division multiple access (OFDMA).

Moreover, the fundamental waveform of NR is cyclic prefix⁃orthogonal frequency division modulation (CP⁃OFDM), while the frame structure and numerology would share some characteristics of LTE.

Innovations in areas of multiple access, channel coding and MIMO will play important roles in achieving 5G performance requirements.

They serve as the main technical drivers to propel the work on basic functionalities listed above such as numerology, frame structures, initial access, and scheduling.

Below Figure shows the framework of NR physical layer technologies.

New multiple access schemes such as those based on non⁃orthogonal properties would introduce a “scheduling⁃light”and/or“light initial access”mechanism to significantly reduce the control overhead and access latency in order to efficiently support mMTC.

New channel coding schemes such as low ⁃ density parity check (LDPC) and polar codes can significantly reduce the decoding complexity for scenarios with large block sizes and/or high coding rates, and improve the performance for those with short block sizes.

It is known that the decoding of channel codes would consume a lot of processing power of a receiver.

Fast decoding also facilitates the design and specification for URLLC. With the super⁃wide bandwidth expected for 5G, i.e., up to 1 GHz, channel codes efficient for large block sizes become an imperative, rather than an option. Without it, frame structure of NR would be merely a hollow place holder.

MIMO techniques help to differentiate NR from 4G in many aspects. NR would operate up to 100 GHz bands. At such high carrier frequency, MIMO or beamforming is a must⁃have feature. Otherwise, the severe path loss and penetration would render NR useless, even indoor.

Hence, beamformed transmission would widely be employed, not only for traffic channels, but also for control signaling, random access signal, synchronization signal, and broadcast channels carrying system information.

References

• J. M Meredith,“Study on channel model for frequency spectrum above 6 GHz,” 3GPP TR 38.900, Jun. 2016
• J. Krause,“Study on scenarios and requirements for next generation access technology,”3GPP TR 38.913, Sept. 2016
• ZTE Corporation