Huawei NearLink Surpasses Bluetooth and WiFi on All Fronts

Huawei NearLink Surpasses Bluetooth and WiFi on All Fronts.

Nearlink may bring the revolution of data connection, and promote more and more devices will abandon wired connection and swift to NearLink Wireless Connection due to longer distance and lower latency.

The NearLink Alliance is jointly initiated by Huawei Technologies Co., Ltd., Adaptrum (USA) Company, and Shenzhen IGRS Information Technology Co., Ltd.

Huawei NearLink Surpasses Bluetooth and WiFi on All Fronts.

People can find “NearLink 1.0 Air Interface Technical Performance Evaluation Report” on the NearLink Alliance website, and compared it with 5G and WiFi.

Here is a brief conclusion:

NearLink has more similarities with 5G than with WiFi, but compared to 5G, it has been greatly simplified (it can be considered to be optimized for a specific scenario based on a certain set of 5G parameters), but it is still better than WiFi in the time domain and The frequency domain scheduling is finer and more complex, and some unique designs of its own have been added.
The single-stream peak throughput of NearLink 20MHz physical layer is similar to that of 5G and WiFi, which can reach about 110Mbps, that is, 5bps/Hz (after considering the control overhead). Due to the introduction of higher 4096QAM, WiFi7 can reach about 160Mbps or 8bps/Hz (regardless of control overhead).
NearLink is closer to WiFi in bandwidth 20/40/80/…/320MHz configuration.
Coding and modulation, MIMO and physical layer HARQ are similar. The main difference is that NearLink uses the Polar code that has not entered the 5G service channel standard in its own service channel, while the 5G and WiFi service channels use LDPC.
Bandwidth efficiency (effective subcarriers) is close to the three: NearLink 93.6%, 5G 95.4%, WiFi 95%.
NearLink sampling rate, OFDM and CP design are very similar to 5G numerology 5.
Judging from the length of NearLink CP, it is obviously shorter than WiFi, so it can be considered that it is mainly used in scenarios with shorter distances than WiFi, such as inside the car and near the human body.
NearLink time-domain scheduling granules, and frequency-domain scheduling granules are closer to 5G (not strictly considered as a special case of 5G). Frequency domain scheduling is finer than WiFi. WiFi is a packet transmission system without strict time-domain granularity.

We don’t know the strategy and vision of the NearLink Alliance. If the industrial ecology grows bigger, it is entirely possible to become the third pole in the field of communication standards alongside the European 3GPP and the American IEEE.

Huawei NearLink Surpasses Bluetooth and WiFi on All Fronts.

The following is a detailed comparison.

– Network Architecture

The basic structure of NearLink is a network of a management node G node and several managed nodes T nodes. In addition, it also supports a single device playing multiple roles to expand the network. This common architecture is also adopted by WiFi and 5G and is no longer expanded.

– Protocol stack architecture

Also follows/maps to OSI 7 layers. This is also the hierarchical structure that is widely adopted at present, and it is no longer expanded.

– 20MHz physical layer single stream peak throughput

NearLink: 115Mbps (1024QAM, coding efficiency 945/1024, throughput depends on control channel overhead, TDD configuration, etc.)
5G: 110Mbps (1024QAM, coding efficiency 948/1024, throughput depends on control channel overhead, TDD configuration, etc.)
WiFi6: 122~143Mbps (1024QAM, encoding efficiency 5/6=853/1024, throughput depends on GI length, control overhead is not considered)
WiFi7: 146~172Mbps (4096QAM, encoding efficiency 5/6=853/1024, throughput depends on GI length, control overhead is not considered)

WiFi throughput is a pure physical layer packet rate, without packet gaps, control packet overhead, etc., so it is higher than NearLink and 5G (unfair comparison). Generally speaking, the peak throughput of each system is similar, and they all take the current physical layer technology to the extreme.

– Physical layer

The minimum NearLink bandwidth is 20MHz, and supports up to 40/60/80/100/160/320MHz. This is very similar to WiFi, and it is not as refined as 5G supports 5/10/15/20/25/…/400MHz on the spectrum where every inch of land is precious.

NearLink CP-OFDM, sampling rate Fs=30.72Msps under 20MHz bandwidth, subcarrier spacing 480kHz, OFDM symbol body contains 64 samples (64-point FFT), CP has two lengths of normal 5 points and extended 14 points. The durations are 69/30.72=2.2461us (where CP length is 5/30.72=0.163us) and 78/30.72=2.5391us (where CP length is 14/30.72=0.456us)

This is exactly the same as the 5G numerology 5 OFDM symbol body configuration: the same sampling rate Fs=30.72Msps, the subcarrier spacing is 480kHz, and the OFDM symbol body contains 64 samples (64-point FFT).

It is very close to the CP length of 5G numerology 5. The extended CP length of 5G numerology 5 is 16 points (14 points for star flash), and the length of normal CP is 4.5 (5 points for star flash). In addition, the 1ms subframe in 5G has two OFDM symbols using 20.5 CP points under the common CP configuration, in order to fill up the 1ms time.

The CP design of NearLink Alliance is more simplified and fixed than that of 5G, making the underlying processing simpler.

In contrast to WiFi, the subcarrier interval before WiFi6 was 312.5kHz, and after WiFi6 and later it was reduced to 78.125kHz (FFT64–>256, symbol body 3.2us–>12.8us). Before WiFi6, the CP length was 0.8us or 0.4us. And later become 0.8/1.6/3.2us. Therefore, the CP length of the NearLink Alliance is obviously shorter than that of WiFi, so it should be mainly used for scenarios with shorter distances than WiFi.

– Number of subcarriers:

NearLink configures 39 subcarriers at 20MHz, a total of 18.72MHz (one of which is an unused DC subcarrier), and the bandwidth efficiency is 18.72/20=93.6%.

5G does not actually support such a small bandwidth of 20MHz when the numerology 5 subcarrier width is 480KHz. A fair comparison is 5G with 15kHz subcarriers at 20MHz. One RB with 12 subcarriers is 0.18MHz, and 20MHz has a maximum of 106 RBs, which is 19.08MHz. The efficiency is 19.08/20=95.4%.

– Frame structure

The wireless frame length of NearLink is 20.833us, and 48 wireless frames form a 1ms superframe. Uplink OFDM symbols, downlink OFDM symbols, and uplink and downlink switching time can be flexibly arranged in each radio frame. However, if the 20.833 wireless frame length directly calculates the number of OFDM symbols, it is not an integer multiple: 20.833/(69/30.72)=9.275 (common CP), 20.833/(78/30.72)=8.2 (extended CP), so only 8 are actually arranged Or 7 OFDM symbol transmission (can be flexibly allocated to uplink/downlink), and the remaining time is used for uplink and downlink switching.

5G also adopts a similar design. The length of the time slot (corresponding to the NearLink wireless frame) is 31.25us, and 32 slots form a 1ms subframe (corresponding to the NearLink superframe). In the case of extended CP, the 1ms subframe will contain 12*32=384 OFDM symbols, exactly 12 OFDM symbols in one slot, and the length of each OFDM symbol (OFDM+CP) is ((64+16)/30.72) us. In the case of a normal CP, a 1ms subframe will contain 14*32=448 OFDM symbols, of which the 0th and 7th*32 OFDM symbols use 20.5 points of CP, and the remaining 14*32-2 OFDM symbols use 4.5 points of CP, Exactly takes up 1ms:

(2*(20.5+64)+(14*32-2)*(64+4.5))/30.72 = 1000us

5G also allows flexible arrangement of uplink and downlink OFDM symbols in a 31.25us time slot.

There is no strict concept of time slot and frame in the WiFi system. It can be considered as a purely packet-based transmission system with more flexibility in uplink and downlink. The number of OFDM symbols contained in the data packet is variable.

– Frequency Domain Scheduling

The minimum granularity of star flash frequency domain scheduling can be a subcarrier 480KHz.

The minimum scheduling granularity of 5G is one RB, that is, 12 subcarriers. The subcarrier width is variable, from 15kHz to even more than 480kHz. Therefore, the scheduling granularity can be smaller or coarser than that of NearLink. 5G is “a single system that supports multiple configuration parameters and adapts to all scenarios.”

WiFi does not support frequency domain scheduling within the 20MHz bandwidth before 802.11ax, and all subcarriers use the same code modulation. For WiFi6 and later, the minimum particle size of RU is 26 subcarriers 2.03125MHz, which is thicker than NearLink and 5G.

– Modulation coding

Star Flash: QPSK/16QAM/64QAM/256QAM/1024QAM. Small packets with ultra-low latency use RS codes, and large packets with large throughput use Polar codes.
5G: BPSK/QPSK/16QAM/64QAM/256QAM/1024QAM. Polar codes are used for control channel packets (replacing the convolutional code TBCC in the LTE era), and LDPC codes are used for traffic channels (replacing the Turbo codes in the LTE era)
WiFi7: BPSK/QPSK/16QAM/64QAM/256QAM/1024QAM/4096QAM. Encodings for large and small packets are not distinguished. BCC convolutional codes can still be used under low throughput, and LDPC codes under high throughput.

The modulation method is similar, except that WiFi7 has an extra 4096QAM.

In terms of channel coding, for Polar codes that have failed to enter the 5G service channel coding standard, NearLink is used for high-throughput and large-traffic service channel coding. In contrast, the main data encoding schemes of WiFi and 5G are both LDPC.

– MIMO

NearLink: G node supports up to 8-stream transmission, and T-node supports up to 4-stream transmission.

5G and WiFi are also similar (with the exception of Massive MIMO).

– Physical layer HARQ retransmission

NearLink: It adopts asynchronous HARQ technology based on Polar code, supports up to 4 HARQ processes, and supports CC-HARQ scheme and IR-HARQ scheme. It looks very similar to HARQ that existed in the LTE era.

5G: It also supports similar asynchronous HARQ, with a maximum of 16 HARQ processes. After all, 5G wants a system to support all scenarios, more processes and more flexibility.

WiFi: WiFi7 began to introduce HARQ similar to LTE. WiFi6 and before have no physical layer HARQ, only MAC layer ACK and retransmission.