Installation Uncertainty of Field Level Calculation around a Base Station Antenna

In the near field, the antenna pattern provided by the antenna manufacturer is generally not applicable, or should be considered with caution, even for the single antenna in free space. In the real life, antenna is often surrounded by other conductive objects in the immediate vicinity. These objects tend to distort the antenna radiation pattern. Since the electromagnetic field calculation for the coverage or radiation hazard analysis depends on the three-dimensional antenna gain, this effect should be taken into account. This paper suggests the use of "installation uncertainty" that should be added to the field calculation. The amount of this quantity depends on the installation geometry and can be calculated numerically for a specific situation. This paper shows the results of numerical calculations for some typical antenna installation geometries

Simple and Low-Cost Realization of RDS Encoder

This paper presents a simple and easy way of realization of RDS encoder. Autonomous equipment which is capable to generate wanted data stream, modulate that data stream and mixed generated signal with stereo or mono FM composite multiplex signal is simulated and produced. Parts of encoder are described, simulated and measured. The use of RDS makes FM receivers more user-friendly. With this simple and cheap RDS encoder, smaller FM broadcasters have a chance to improve business ability

Prostorno-frekvencijsko blok kodiranje sa odsjecanjem i filtriranjem kao tehnika predajni diverziti u SC-FDMA

The paper presents Space-Frequency Block Coding (SFBC) as a transmit diversity technique in Single Carrier Frequency Division Multiple Access (SC-FDMA). SC-FDMA is known as a low Peak-to-Average Power Ratio (PAPR) modulation technique. SFBC requires changing the order of the samples in the frequency domain, which results in increase of the PAPR. Because of that, additional clipping and filtering is proposed to be performed after SFBC to preserve low PAPR level and to avoid the out-of-band radiation. This affects the performance, but still provides significant advantage to the existing techniques, as is shown using simulationsOvaj papir predstavlja prostorno-vremensko blok kodiranje (SFBC) kao tehniku predajnog diverzitija u Single Carrier Frequency Division Multiple Access (SC-FDMA) sustavima. SC-FDMA je poznat kao modulacijska tehnika sa niskim omjerom vršne i srednje snage (PAPR). SFBC zahtjeva izmjenu redoslijeda uzoraka u frekvencijskoj domeni, što rezultira povećanjem PAPR-a. Zbog toga, dodatno odsjecanje (clipping) i flitriranje signala nakon SFBC-a je predloženo u cilju očuvanja niske vrijednosti PAPR-a i izbjegavanja zračenja van opsega. Ovo utječe na performance, ali idalje pruža značajnu prednost nad postojećim tehnikama, kao što je pokazano kroz simulacije

Radiation Hazard Aspect of Shipboard Radiocommunication Equipment

The paper analyzes the electromagnetic (EM) radiofrequency (RF) radiation hazards onboard a ship arising from shipboard radiocommunication and navigation equipment. EM field effect on personnel and equipment can be harmful if field levels exceed the threshold values. These fields need to be controlled for proper protection. Ships are equipped with lots of EM RF radiation sources with different frequencies and output power levels. Typical shipboard EM RF radiation sources include: terrestrial radiocommunication transmitters, navigational radars and satellite ship earth stations (SES). Examples of these sources are analyzed in the paper. EM field estimation using simple worst-case calculation is given for a typical HF transmitter, X-band navigational radar and the Inmarsat SES A, B, C, F and M. The estimation problems are discussed. The calculation results are compared with international civil and military standards. The results show that potential hazards exist and that a reasonable amount of caution is needed

Algoritam alokacije resursa s dinamičkim pridruživanjem podnosioca u bežičnim mrežama zasnovanim na OFDMA-u

The allocation of available resources is one of the main issues in multi-user systems. Dependence of system capacity on radio link quality is an additional obstacle of efficient resource allocation in wireless networks. Combinations of two opposite approaches -- fair resource allocation and system capacity maximization are used to solve this problem in practice.This paper proposes a resource allocation method that is primarily based on assigning almost an equal bandwidth to all users. System capacity maximization is achieved by selecting the subcarriers with the best SNR values. This algorithm was developed for orthogonal frequency division multiple access (OFDMA) wireless systems. Resource allocation is done at the subcarrier level according to the weight factor that had been calculated for each user. Frequency hopping was used to increase frequency diversity and to make the system more robust to disturbance. Frequency hopping pattern is determined dynamically on the basis of SNR value of each subcarrier.The results of the proposed algorithm are compared with the water filling (WF) and proportional fairness (PF) methods. The influence of various data traffic classes on system throughput and resource allocation is also described.U sustavima s više korisnika jedno od glavnih pitanja je kako podijeliti raspoložive resurse. Kod radio mreža dodatni otežavajući faktor predstavlja promjenjivost kapaciteta sustava ovisno o kvaliteti radio veze. U praksi se za raspodjelu resursaobično koriste algoritmi koji su kombinacija dvaju oprečnih pristupa, fer raspodjele resursa i maksimizacije kapaciteta sustava.U ovom radu predložena je metoda primarno bazirana na fer raspodjeli resursa. Maksimizacija kapaciteta sustava ostvarena je odabirom podnosilaca s najboljim mogućim SNR-om. Algoritam je razvijen za sustave bazirane na OFDMA. Dodjela resursa korisnicima vrši se na razini pojedinog podnosioca prema izračunatom težinskom faktoru za svakog korisnika posebno. Kako bi se povećao frekvencijski diverziti i sustav učinio otpornijim na smetnje, uvedeno je frekvencijsko skakanje prema dinamički određenom predlošku. Predložak se formira na osnovu SNRvrijednosti određene po svakom podnosiocu. Rezultati predloženog algoritma uspoređeni su s WF (water filling) i PF(proportional fairness) algoritmima. Prikazan je utjecaj različitih klasa prometa na prijenosni kapacitet i raspodjelu resursa sustava

Brzi paketni pristup

Data services and multimedia are expected to have significant growth over the next few years and will likely become the dominant source of 3G traffic. High Speed Downlink Packet Access (HSDPA) provides large enhancements over Wideband Code Division Multiple Access (WCDMA) for the downlink. HSDPA was standardized as part of Third Generation Partnership Project (3GPP) Release 5 and improved in later releases. The HSDPA peak date rate available in the terminals was initially 1.8 Mbps, but it has increased to 42 Mbps. HSDPA has been designed to increase downlink packet data throughput by means of fast physical layer retransmission and transmission combining as well fast link adaptation controlled by the Node B – i.e. a base transmission station (BTS). High Speed Uplink Packet Access (HSUPA) was part of 3GPP Release 6 with the first specification version in December 2004. The HSUPA peak data rate in the initial phase is expected to be 1–2 Mbps with later phase pushing the data rate to 11.5 Mbps. HSDPA and HSUPA together form High Speed Packet Access (HSPA).Očekuje se da će podatkovne usluge i multimedija imati značajan rast te će vjerojatno postati dominantan izvor 3G prometa u sljedećih nekoliko godina. Brzi paketski pristup u silaznom smjeru (HSDPA) pruža veliko unaprjeđenje u usporedbi sa na širokopojasnim višestrukim pristupom po kodnoj raspodjeli (WCDMA) za silazni smjer. HSDPA je normiran kao Release 5 od strane 3GPP te je unaprjeđivan u daljnjim izdanjima. U početku je raspoloživa brzina prijenosa podataka u korisničkim uređajima iznosila 1,8 Mbit/s, ali je sad povećana na 42 Mbit/s. HSDPA je osmišljen kako bi povećao brzinu prijenosa podataka u silaznom smjeru te pritom se koristi tehnikama brzog ponovnog slanja podataka na fizičkom sloju, brzom prilagodbom veze u baznoj postaji, itd. Brzi paketski pristup u uzlaznom smjeru pojavio se kao dio 3GPP Relase 6, a izišao je u prosincu 2004. U početnoj fazi HSUPA je omogućavala vršne brzine prijenosa podataka od 1 do 2 Mbit/s, dok trenutno omogućava brzine prijenosa podataka od 11,5 Mbit/s. Obje tehnologije, HSDPA i HSUPA zajedno, nazivaju se brzi paketski pristup (HSPA)

PHY, MAC, and RLC Layer Based Estimation of Optimal Cyclic Prefix Length

This work is motivated by growing evidence that the standard Cyclic Prefix (CP) length, adopted in the Long Term Evolution (LTE) physical layer (PHY) specifications, is oversized in propagation environments ranging from indoor to typical urban. Although this ostensibly seems to be addressed by 5G New Radio (NR) numerology, its scalable CP length reduction is proportionally tracked by the OFDM symbol length, which preserves the relative CP overhead of LTE. Furthermore, some simple means to optimize fixed or introduce adaptive CP length arose from either simulations or models taking into account only the bit-oriented PHY transmission performance. On the contrary, in the novel crosslayer analytical model proposed here, the closed-form expression for the optimal CP length is derived such as to minimize the effective average codeblock length, by also considering the error recovery retransmissions through the layers above PHY—the Medium Access Control (MAC) and the Radio Link Control (RLC), in particular. It turns out that, for given protective coding, the optimal CP length is determined by the appropriate rms delay spread of the channel power delay profile part remaining outside the CP span. The optimal CP length values are found to be significantly lower than the corresponding industry-standard ones, which unveils the potential for improving the net throughput

Efficient Estimation of CFO-Affected OFDM BER Floor in Small Cells with Resource-Limited IoT End-Points

Contemporary wireless networks dramatically enhance data rates and latency to become a key enabler of massive communication among various low-cost devices of limited computational power, standardized by the Long-Term Evolution (LTE) downscaled derivations LTE-M or narrowband Internet of Things (NB IoT), in particular. Specifically, assessment of the physical-layer transmission performance is important for higher-layer protocols determining the extent of the potential error recovery escalation upwards the protocol stack. Thereby, it is needed that the end-points of low processing capacity most efficiently estimate the residual bit error rate (BER) solely determined by the main orthogonal frequency-division multiplexing (OFDM) impairment–carrier frequency offset (CFO), specifically in small cells, where the signal-to-noise ratio is large enough, as well as the OFDM symbol cyclic prefix, preventing inter-symbol interference. However, in contrast to earlier analytical models with computationally demanding estimation of BER from the phase deviation caused by CFO, in this paper, after identifying the optimal sample instant in a power delay profile, we abstract the CFO by equivalent time dispersion (i.e., by additional spreading of the power delay profile that would produce the same BER degradation as the CFO). The proposed BER estimation is verified by means of the industry-standard LTE software simulator

Efficient Estimation of CFO-Affected OFDM BER Floor in Small Cells with Resource-Limited IoT End-Points

Contemporary wireless networks dramatically enhance data rates and latency to become a key enabler of massive communication among various low-cost devices of limited computational power, standardized by the Long-Term Evolution (LTE) downscaled derivations LTE-M or narrowband Internet of Things (NB IoT), in particular. Specifically, assessment of the physical-layer transmission performance is important for higher-layer protocols determining the extent of the potential error recovery escalation upwards the protocol stack. Thereby, it is needed that the end-points of low processing capacity most efficiently estimate the residual bit error rate (BER) solely determined by the main orthogonal frequency-division multiplexing (OFDM) impairment–carrier frequency offset (CFO), specifically in small cells, where the signal-to-noise ratio is large enough, as well as the OFDM symbol cyclic prefix, preventing inter-symbol interference. However, in contrast to earlier analytical models with computationally demanding estimation of BER from the phase deviation caused by CFO, in this paper, after identifying the optimal sample instant in a power delay profile, we abstract the CFO by equivalent time dispersion (i.e., by additional spreading of the power delay profile that would produce the same BER degradation as the CFO). The proposed BER estimation is verified by means of the industry-standard LTE software simulator