5.8 GHz


The 5.8 GHz band is the best choice in terms of price and accuracy for real-time location system

The use of higher frequencies for location applications such as tracking of people and equipment has many advantages over other frequencies. Systems built on higher frequencies provide a reduction in production costs and high-speed transport data between the badges, tags and receivers. In addition, they offer the best compromise to transmit a wireless signal, by leaky wave, by reflections in crowded spaces such as a refinery. The use of higher radio frequencies offers the ability to manufacture small devices with unparalleled efficiency for real-time location systems (RTLS) and active RFID tags. The physics of wireless technology shows four main factors affecting the quality of communication and system performance:

  1. 1. Traffic in the band
  2. 2. Problems of propagation and behavior when faced with obstacles and depending on the distance
  3. 3. Spectral efficiency
  4. 4. Device effectiveness

1. Traffic in the band

High Traffic in 433 MHz, 900 MHz and 2.4 GHz bands

433 MHz, 900 MHz and 2.4 GHz bands are widely used in consumer devices such as monitors, ovens, microwaves, Bluetooth, local communication devices. 433 MHz band has been used for decades for short-range communications. However, these RFID networks operating in these bands suffer from disturbances in the low frequency signals from other wireless devices.

The higher traffic in the band, the higher the receptor complexity must be to reject noise and interference and maintain signal quality. The result is an increase in complexity and price of the unit. It is therefore better to use an uncluttered and larger band as the 5.8 GHz band, to better manage large capacity real-time location systems, such as Purelink RTLS.

2. Problems of propagation and behavior when faced with obstacles and depending on the distance

Better signal propagation characteristics at 5.8GHz

Most short-range communications occur around human structures, such as vehicles and buildings. For middle ranges in distances of 0-1 km and for the same level of transmitting power, the 5.8 GHz band has almost the same communication range as the 433 MHz band.

The 5.8 GHz band offers a Fresnel diffraction zone the smallest compared to the bands 433 MHz, 900 MHz and 2.4 GHz. Because of its shorter wavelength, the signal at 5.8 GHz can pass through the narrowest of spaces. At the same time, it maintains its ability to penetrate through almost similar materials such as waves in the 433 MHz band. Therefore, when the waves at 433 MHz are blocked or diffracted by obstacles, due to the signal wavelength of more than 70 cm, the signal at 5.8 GHz can easily pass through these obstacles because of its very short wavelength of only 5.17cm.

The wavelength of the signal determines the device size and performance. Therefore, in general, products exploiting the high frequencies are more compact and have better efficiency.

Frequency Wavelength
5.8 GHz 5.17 cm
2.4 GHz 12.5 cm
900 MHz 32.7 cm
433 MHz 69.3 cm

Frequency Distance
5.8 GHz with direct spread spectrum 100 - 670 m (300 - 2000 pi)
2.4 GHz with direct spread spectrum 100 - 670 m (300 - 2000 pi)
900 MHz with direct spread spectrum 100 - 500 m (300 - 1500 pi)
433 MHz 25 - 133 m (75 - 400 pi)

At 5.8GHz, the wavelength being shorter, the antennas are smaller, the penetration through holes in obstacles and the transmission by leaky waves are better. In addition, the components used in 5.8 GHz badges or tags are smaller and more energy efficient.

The propagation characteristics of signals at 433 MHz, 900 MHz, 2.4 GHz and 5.8 GHz in free space are similar in situation of rain. This is important to consider in tropical climates and continental for outdoor applications.

The figure below shows how the propagation at long range, for almost all frequencies below 10 GHz, is affected the same way for different types of rain conditions. Under heavy rain, all frequencies below 10 GHz suffer nearly 0.1 dB of attenuation per kilometer of propagation. real-time location systems in are generally built with tag / receiver lines of communication of less than 500 m. Therefore, one should consider the frequency effectiveness, noise in the communication band and interference to select the best frequency for your location-based applications or active RFID tags.

figure 1
RF signal propagation and atmospheric attenuation for different frequency bands

The 5.8 GHz band offers a range of communication similar (0-1 km) than other low frequency bands. However, at 5.8 GHz, the error rate per bit transmitted (BER) is much lower due to a less crowded bandwidth. The 5.8 GHz ISM band offers 75 MHz bandwidth communication. This is almost twice the bandwidth of 2.4 GHz band. This results in more energy-efficient products with higher data rates.

3. Frequency efficiency

High data rate modulation at 5.8 GHz

The data transfer rate is greater at 5.8 GHz because the frequency is higher. This is very important when it comes to track, locate and communicate with hundreds of badges and tags in motion, such as people, equipment, vehicles or containers. Purelink location system allows to track a vehicle traveling at a speed exceeding 200 km / h without problems of communication between the tag associated with the vehicle and the receptors located more than 200 meters from the road. The Doppler Effect may be important in systems with low frequency because of the slower modulation techniques in the bands 433 MHz, 900 MHz. However 5.8 GHz tags can be read at speeds of 250 km / h without any misreading, even if the tag is hidden in the trunk!

The 5.8 GHz band provides data rates from over 2 Mb / s to 100 Mb / s. The advanced modulation techniques can provide important data rates for real-time location systems such as the one manufactured by Purelink. When it comes to implementing security applications, applications for protection of people or commercial applications requiring high reliability, high accuracy and reasonable cost, Purelink location systems are the most effective.

A higher modulation at 5.8 GHz can transmit large amounts of data. In many industrial applications where a real-time location system is required to process each second the position and status of hundreds of workers with an average error of ± 2 meters, only Purelink location system can meet the task.

Location systems at low frequency of 433 MHz, 900 MHz and 2.4 GHz cannot handle the large data rate modulation and they cannot provide consistency, robustness, accuracy and throughput.

4. Device efficiency

Better electronics design at 5.8 GHz

At 5.8 GHz, the ability to use transmission lines for antenna design leads to cheaper solutions with smaller circuit boards. The result is a device very compact, lower cost and greater energy efficiency.

Using the 5.8 GHz band provides the opportunity to make tags in a single chipset. The results are devices smaller and lighter, and a considerable increase the device energy efficiency.

At 5.8 GHz, the antennas are smaller and can be produced in a variety of forms.

The 5.8 Ghz band is compatible with CMOS technology

CMOS technology has many advantages:

  • Mature technology
  • Low bias voltage (<3V, even below 1V for SOI MOS)
  • Low power consumption (portable applications)
  • Possibility to build a single chip with both analog and digital circuits
  • High level integration possible
  • Compatible with micromachining techniques (MEMS)

The result is a great technological superiority of devices at 5.8GHz such as Purelink technology.

Comparison of usual bands
Frequency Advantages Drawbacks High Traffic
418 MHz
433 MHz
868 MHz
915 MHz
  • Good communication range
  • Good water/body penetration
  • Band authorized in many countries
  • Big devices and antennas
  • High energy consumption
  • Low integration of componenets
  • Limited transmission rate
  • Compact devices and antennas
  • Good communication range
  • High transmission rate
  • Sensitive to noise
  • Require sensitive receivers
  • High energy consumption
  • Require frequent battery changes
  • Expensive
  • Poor water/body penetration
  • Very compact devices and antennas
  • High energy and spectral efficiency
  • Very good communication range
  • Very high transmission rate
  • Can be build in one chip
  • Require sensitive receivers
  • Poor water/body penetration

Performance table
DILS WiFi Short range active RFID
Characteristics 5.8 GHz 2.4 GHz 1.2 GHz 900 MHz UHF
Available channels 8-16-32 4 4 3 Multiple
Interference risk Very low High Medium Medium Medium
Band type FM FM FM AM AM
Resolution Excellent Excellent Excellent Good Medium
Range Long Medium Medium Short Short
Outdoor performance Excellent Excellent Excellent Good Medium
Position accuracy (X,Y) Excellent Low Low Low by Zone
Security Excellent Good Good Medium Low
Licence required No No Yes Yes No
Penetration capability :
Water/Body Low Low Good Good Good
Wood Medium Medium Good Very Good Excellent
Concrete Medium Medium Good Very Good Excellent
Tinted window Low Low Low Low Low
Metal No No No No No