## 1 Introduction  
5G is a major technological step forward in communication systems [1]. It has introduced a number of new solutions at the physical layer [2; 3; 4], sophisticated active large antennas [5; 6; 7; 8], and massive MIMO technology [9; 10; 11] that take advantage of the presence of scattering objects to obtain multiple spatial channels. The introduction of such technologies has prompted extensive research activity on new large antenna synthesis methods [12; 13; 14; 15] and highly precise numerical methods for scattering estimation [16; 17] even in anticipation of their use at very high frequencies [18; 19]. However, this new technology represents a formidable challenge for the field of human exposure assessment. Recommended methods for RF exposure are specified in [20]. The document includes three main RF exposure evaluations: product compliance (i.e., determination of the compliance boundary information before the product is placed on the market), product installation compliance (i.e., determinations of the total RF exposure level before the product is put into service) and in situ RF exposure assessment (i.e., after the product has been put into service). In particular, in [20], the extrapolation of the exposure at the network maximum traffic load and MPE techniques have been introduced. They use a reference signal transmitted at maximum power to estimate the maximum field level assuming that all the resources of the communication system are assigned to a single user. This value is then multiplied by a proper \(F_{PR}\) factor according to ([20] clause B5). Many effective solutions for 5G MPE have been proposed in the literature [21; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31; 32], which allow accurate assessment of the field level at the measurement point in currently used 5G systems. They mostly deal with the estimation of the boost factor of traffic beams with respect to broadcast beams (called \(F_{beam}\) below; see Section 2). However, the proposed measurement techniques require an active interaction with the gNB and/or expansive measurement setups. In this paper, we investigate the use of the envelope radiation patterns [33; 34] to obtain a conservative value of the field level at the measurement location. The method is based on a Maximum Power Extrapolation approach. It allows a conservative value of the RF exposure level to be obtained and can be applied to both product compliance and product installation compliance in order to determine if the RF exposure levels are in compliance with exposure limits and regulations. It requires the measurement of a reference quantity associated with the SS-PBCH (such as PSS, SSS, PBCH, or PBCH-DMRS). This step requires a simple spectrum analyzer and allows the Resource Element (RE) power of a signal transmitted through the Broadcast beam to be obtained. A cheaper approach based on the use of a calibrated cell phone to obtain SS-RSRP can also be followed. In the second phase, the field level is estimated using the CDF of the antenna boost factor obtained from the broadcast and from the traffic envelope radiation patterns made available by the base station vendor [33]. The use of the CDF allows mitigating the problems related to the exact estimation of the direction of the measurement point with respect to the beam of the 5G antenna. The method is applied to a real 5G communication system, and the result is compared with the value given by other MPE methods proposed in the literature. The value obtained with the procedure described above is an upper bound with a high probability of the maximum field value. The paper is organized in the following way. Section 2 introduces the MPE procedure for 5G systems, recalls techniques for antenna boost factor estimation from measurements, and introduces the technique for antenna boost factor estimation from the envelope radiation patterns. Section 3 describes the MPE procedure based on the antenna boost factor estimated from the envelope radiation patterns. Section 4 presents an experimental validation of the method.