RS-422 Utility

In cases where a computer and the device to be communicated with are much far apart, RS-422 is the preferred serial standard. Due to differential signaling, the signal is less prone to noise and may be sent on cables as long as 1500 meters. Maximum data rate is 10 Mbps at 12m and degrades with cable length. You can use a commercially available USB-422 adapter or make one yourself to send and receive RS-422 signals on your computer. 

DC-DC Converter

Portable electronic devices often contain several sub-circuits, each with its own voltage level requirement different from that supplied by the battery. Here a DC-DC Converter is used to provide the required voltage conversion. Traco Power, Maxim Integrated, Texas Instruments and Fujitsu are some of the manufacturers of DC-DC Converter ICs.

Frequency Hopping

GSM and DCS both employ frequency hopping technique for two main advantages:

• To reduce Mulitpath Fading effect which is dependent in carrier frequency
• To randomize Co-Channel Interference (CCI)

The hopping algorithm is continuously broadcast on BCCH and MS/BTS transmits TDMA frames on different hopping carriers during a call on hopping TRX. Hopping is used on TCH, SDCCH and all Packet Data channels while BCCH and common control channels are not allowed to hop. Frequency hopping types are:

• Baseband Hopping (BBH)
• Synthesizer Hopping (SFH)
• Discrete Hopping

Sector Swap Issue in a Cellular Network

Sector Swap issue refers to the situation when cables of connected to wrong antennas, for example, sector 2 cables are connected with the sector 1 antenna and sector 1 cables are connected to sector 2 antenna. This issue can cause degraded quality, call drop, illogical hand over etc.

Power Control RxLev for GSM and DCS

The upper and lower bounds of Power Control RxLev for Downlink should be set such as signal strength is maintained slightly above the threshold of noise floor. This would provide for enough signal strength to maintain a good voice quality and keeping the interference level to the minimum. Thus, these values are kept more aggressive for DCS, being a clearer band than GSM, for instance, the upper and lower bounds for DCS are generally set to -80dBm and -90dBm as compared to GSM values of -75 dBm and -85 dBm.

Antenna Tip of the Day!

Omni-directional antennas have the advantage of more coverage while directional ones provide higher gain. Phased arrays combine the advantages of both of these by providing higher gain in all directions turn by turn. 

Array Signal Processing

Methods used to estimate the Angles of Arrival (AoA) of signals at a base station can be generally classified into two categories.

1. Maximum Likelihood Based Algorithms
2. Subspace Estimation Based Algorithms

MUSIC (Multiple Signal Classification) is one of the methods based on subspace estimation that can be used to estimate the angles of arrival of multiple impinging signals. In this method array of antenna elements is used, all the impinging wave fronts are recorded on all antennas and processed to find out the angles of arrival. Maximum number of impinging wave fronts that can distinguished using this method is given by M-1, where M is the number of elements in the antenna array. The reason is that this method is based on Noise Subspace and we need at least one vector for noise subspace to exist, which is made sure when the number of impinging wave fronts is at least one less than the number of antenna elements in the array.

Antenna Tip of the Day!

A radome becomes completely reflection-less if its thickness is half the wavelength.

GPRS and EGPRS

As per The European Telecommunications Standards Institute (ETSI), GPRS has 4 coding schemes namely CS-1, CS-2, CS-3 and CS-4. CS-1 offers lowest data rate with highest data protection whereas CS-4 has highest data rates with minimal protection of data. E-GPRS uses 8-PSK modulation (transmits 3 bits per symbol) scheme and consequently has 9 coding schemes MCS-1 to MCS-9 in order of highest to lowest data protection and lowest to highest data speeds.

Antenna Tip of the Day!

When a Right Handed Circularly Polarized (RHCP) wave strikes a plane surface, it becomes LHCP on reflection. In case when it strikes a corner reflector, it retains its polarization (due to dual reflection).

Team Management

"Coutesy www.managementstudyguide.com" Management is essential in every walk of life. Even what we eat should be managed. You just can’t put anything in your mouth. One needs to be cautious. In the same way, a team must be managed effectively to expect the best from the team members. The team leader plays an essential role in managing his team well. ■For effective team management, it is important that the team leader is more of a mentor to his team members rather than just being a strict boss. Understand your team members well. Gone are the days when people used to fear their bosses. Now a days employees share a healthy relation with their superiors and the comfort level has increased to a large extent. Don’t impose things on them. ■Ensure that each and every team member willingly participates in team discussions. Debates are important, but make sure you don’t end up fighting with each other. Suggestions must be invited from all and do not discuss issues separately with individuals. Call every one on an open forum and formulate strategies keeping in mind every body’s inputs. Poilcies should be made best suited to all. The objective of the team must be clearly set and circulated among all the team members. Everyone should be aware of his roles and responsibilities in the team. ■Communication among the team members must be clear and transparent for an effective team management. Every team member should get the same information and should have an easy access to the superiors in case of any query. ■The team members must not pass on any information to anyone outside the team. Learn to keep things to yourself. It is unethical to share your professional secrets with others. Don’t leak information or any confidential data. ■The team members must be motivated on a regular basis. Appreciation is a must. If any team member has performed extraordinarily, do give him a pat on his back. Performance appraisals, perks, incentives, trophies, prizes are all instrumental in motivating the team members to perform even better the next time. Avoid criticizing any of your team members. ■Loose talks, blame games, dirty politics should find no place in the team. They spoil the environment and people lose interest in their work and organization. If you come to know anything about someone, it’s better to discuss with him face to face, else ignore. ■It is easy to create a team but it is actually difficult to bind the team members together and even make them work. Team management techniques help in strengthening the bond among the employees and creating an environment where they can trust each other. People actually become friends and start working together as a result of team management activities.

Antenna Tip of the Day!

Circularly polarized antennas find their application in ground stations for receiving signals from bodies having arbitrary motion and mounted with linearly polarized antennas. This is done so that the maximum polarization loss at any instant doesn't exceed 3 dB.

Antenna Tilts

There are two types of antenna tilts used in telecom networks:

1. Electrical Tilt
2. Mechanical Tilt

Electrical Tilt has a uniform affect on the main lobe whereas Mechanical Tilt causes side lobe effect when it is given a down tilt. The effect can be demonstrated easily on Coverage Planning tools.

Antenna Tip of the Day!

The polarization loss between a perfectly circularly polarized antenna and a linearly polarized (in any direction) antenna is 3 dB.

Antenna Tip of the Day!

Another way of increasing a Microstrip Antenna's bandwidth is using an aperture coupled feed.

Antenna Tip of the Day!

Microstrip Antennas generally have a narrow bandwidth. One of the ways to increase their bandwidth is to introduce air gap between substrate and the ground plane.

SMS Transfer during a Call

SACCH is also used for SMS delivery when a call is in progress.

Antenna Tip of the Day!

Bandwidth of Wire Antennas can considerably be increased by making them conical in shape.

Antenna Tip of the Day!

Bandwidth of wire antennas such as monopole and dipole can be increased by increasing their diameter.

Antenna Tip of the Day!

A criteria generally used for antenna designs is a VSWR <= 2 or a Return Loss >= 10 dB over the desired frequency band. In this case the power delivered to the antenna will be 89% or more across the whole band. 

Handover Optimization in GSM

Optimizing Handover procedures in a telecom network helps a great deal in decreasing call drop rate, increasing HSR and thus improving mobility and quality of the network. Handover parameters like RxQual thresholds at which handover should be triggered, timers that control the repetition of Handover requests to neighbour cells, penalty on source cells to curb the handover requests on congested cells are some of the areas that create a significantly positive impact on network KPIs.

Fast Drive Investigation (FDI)

Fast Drive Investigation (FDI) is a post processing tool developed by engineers of Pakistan. It is the only product in the field of  RF Optimization fully developed locally by a team of experienced engineers. The tool is in use by telecom operators in Pakistan and Afghanistan and has received tremendous appreciation and acclaim for its world-class algorithms and convenience. The features of the product include overshooters identification with footprints, quick neighbor audit feature, mesh analysis for multi-server environment, low-coverage zones depiction, graphical analysis of various KPIs etc with a standard comparable to international software. Other tools advantageous for Optimization engineers are also included in their product line. More on this can be read from their website. Trial version of the software is not available which needs to be developed to increase its propagation and usage worldwide.

More here: 360cellutions.com 

Antenna Tip of the Day!

Gain is the product of directivity and radiation efficiency only. If Gain is multiplied by the reflection efficiency, it becomes Absolute Gain (called Realized Gain in HFSS).