ESTIMATION OF POTENTIAL PARAMETERS FOR 5G MOBILE NETWORKS RADIOCHANNELS

Background. Deploying of 5G mobile networks opens up wide opportunities for the development of IoT, high-speed access to Internet services, industrial automation, telemedicine and other modern services. Peak transmission rate, latency, and spectral efficiency are important indicators for network performance. These indicators are primarily determined by the 5G-NR radio subsystem, which is built using modern technologies such as OFDM, interference-resistant LDPC coding and massive MIMO antenna systems. In addition, frames and time-frequency resource distribution in 5G-NR are improved for both Downlink and Uplink. All of these are described in various 3GPPP documents, but to evaluate these indicators, it is necessary to create an appropriate methodology and perform calculations. Objective. The purpose of the research is to create a methodology and estimate the potential values of peak transmission rate, latency and spectral efficiency of 5G-NR radio channels. Method . Analytical calculation methods based on recommendations and source data of 3GPP documents are used. Results. Analytical studies show that 5G-NR radio channels can potentially provide a peak transmission up to 37 Gbps, latency less than 0.5ms, and spectral efficiency up to 46 bps/Hz rate in the Downlink direction using 50 MHz FR1 frequency band, QAM256 modulation and MIMO 8 x 8-antenna system. Conclusions. The researched 5G-NR radio channels efficiency indicators meet current and future services requirements.

The creation of radio channels in the 5G mobile communication network takes place due to use the modern technologies such as OFDM and massive MIMO. Also optimized frames and improved distribution of time-frequency resources on both Downlink and Uplink. All of these technologies are used in the 5G-NR (5G -New Radio) and described in 3GPP documents as radio interface specification. Peak transmission rate, latency and spectral efficiency are very significant among the key indicators (KPI) which define the quality of radio channels. Therefore, research was performed specifically for these indicators.
According to the recommendation of the 3GPP document [1], the estimated common peak transmission rate in the Downlink direction can be calculated using the formula: ��� �����,� -the maximum number of resource blocks in the used frequency band; ОН (Over Head) -the proportion of time spent on service data in the Downlink direction. OverHead is equal 0.14 for the FR1 band (410…7125 MHz) and equal 0.18 -for the FR2 band (24250…52600 MHz).
The number of resource blocks that can be used in a frequency band depends on subcarrier channel space and frequency band [2].   5  10  15  20  25  30  40  50  60  80  90  100  15  25  52  79  106  133  160  216  270  ----30  11  24  38  51  65  78  106  133  162  217  245  273  50  -11  18  24  31  38  51  65  79  107 121 135   The peak transmission rate is up to 275 Gbps and is achieved when using the SCS of 120 kHz, the number of aggregated components carriers is 16, and a total frequency band of 400 MHz At this time continue the work to allocate part of the 700 MHz band in Ukraine, which is currently occupied for television. Also band 3400...3600 MHz unlocked now (part of the FR1 band). Thus, the frequency band for the operation of 5G networks in Ukraine is 200 MHz. If we consider that the 4 largest operators of Ukraine can potentially apply for this band, then the frequency band for each of them can be allocated in the amount of 50 MHz. According to calculations ( Fig. 1), this can potentially provide a Downlink peak transmission rate up to 37 Gbit/s for each operator's network.
The transmission latency for the user plane is defined [5] as the delay in data transmission between the gNB and the UE (User Equipment), i.e. the time from the moment the IP packet is transmitted to the moment when the receiver successfully receives the IP packet and delivers the packet to the upper layer. The input data to make a latency calculation method are given [4]. The model for latency is described in [5] and shown on  The latency � � consists of payload packet transmission delay (τ1), Hybrid Automatic Repeat Request (HARQ) retransmission delay (τ2) and payload packet retransmission delay (τ3). The latency according to the given model can be determined as follows: where: -retransmission probability.
The payload packet transmission delay � can be calculated according to the following formula: where: ���,�� -packets processing duration in gNB; tFA1 -time interval needed for frame alignment or it is a time to wait next DL (Down Link) slot; tTTI -data transmission duration; tUE,rx -packet processing duration in UE (interval between packet receiving and packet full decoding).
The duration of packet processing in the base station can be calculated according to the following formula: wherе: N2 -the duration defined in the number of OFDM symbols needed for preparing the PUSCH (Physical Uplink Shared Channel) signaling messages [4], κ = 64 -constant; Tc= 1/(∆fmax ꞏNf) -number of time units . As defined in [3] ∆fmax always equal 480 x10 3 Hz and Nf= 4096.
N2 parameter depends on SCS and has the following value (Table 3): It should be noted that the delay in the gNB is the same during transmission and reception. This also applies to the delay in the UE (user device). Therefore, the processing time can be calculated as follows: where: N1 -PUSCH-message processing duration.
In case of reception errors, a request for retransmission using a HARQ packet is formed on the UE side, which requires the following time: where: ��� -frame alignment time duration; ���� -request duration, which equal one OFDM symbol duration.
After receiving and processing the HARQ request, the gNB retransmits the content of the IP packet. Duration for retransmission will be as following: In the third step, the gNB again takes a time to process the transmission with the same value of 178.4 µs. The frame alignment time in this case is 357 µs. In either case to reach the first symbol of the subframe and retransmit the packet. The TTI is retransmitted in 1 ms and the UE processes the data in 107 µs. The total retransmission time τ3= 1.64 ms for the 15 kHz SCS.
According to mentioned above method was calculated the latency for all possible SCS and re-request probabilities of 0; 0.1 and 1. The calculation results are shown in Table 5. Table 4. N1 -PUSCH-message processing duration -peak transmission rate (1); coefficient of frequency resources utilization; -frequency band used in the network.
Calculation results of � in bps/Hz for QAM256 modulation are shown in Table 6.