411 on DAS

September 28, 2017 at 8:00 AM

 

If you’ve ever lost your cellular signal in a building that you thought would be covered by your cellular network, you probably would have appreciated the help of a distributed antenna system (DAS). Today’s construction techniques and materials block or weaken internal and external wireless communication signals inside buildings. Blocked radio and cellular reception isn’t only a nuisance for consumers, it can be detrimental to public safety and hinder first responders in an emergency situation. Thus, distributed antenna systems were designed to counteract those effects and extend wireless coverage within structures to allow radios and cell phones to work everywhere within the building.

 

A distributed antenna system uses several small antennas, as opposed to one antenna, to provide wireless coverage and eliminate spots of poor coverage inside a large building. These antennas serve as repeaters and provide reliable coverage within the structure, without requiring much additional power. They provide voice and data services, just like a cellular tower would, without any noticeable difference to mobile device reception. Any densely populated indoor space is a good candidate for DAS deployment, such as shopping malls, medical centers and high-rise buildings. Distributed antenna networks also provide wireless coverage to hotels, subways, airports, hospitals, businesses, roadway tunnels and more. In addition to indoor use, a DAS can be designed to extend wireless coverage for outdoor use. Distributed antenna systems typically provide wireless services that include PCS, cellular, Wi-Fi, police, fire and emergency services.

 

A DAS often uses RF directional couplers and/or wireless amplifiers to split and amplify the wireless signal from the source to the distributed antennas. In many cases, a DAS will use a combination of low-loss coaxial cabling as well as fiber optic cabling to support radio-over-fiber (RoF) technology and distribute the wireless signals to the antennas. The antennas are physically connected to a central controller, which is then connected to the wireless carrier network’s base station. At least one carrier network must be involved with a DAS deployment because the systems operate on the RF spectrum, which is licensed to wireless carriers.

 

Distributed antenna systems can be passive or active. A passive DAS grabs cellular signals from roof antennas and runs them through leaky feeder cables that distribute the signal throughout the building. An active DAS passes the signal from the roof antennas through fiber cables, boosting and amplifying the signals as needed.

 

Deploying DAS is the most expensive aspect of the project, as it can be very labor intensive to install the antennas and run cables between antenna modules and the controller. Usually, the carrier network manages the cost and maintenance of the DAS system, as long as it aligns with their network plan and fills a significant gap in service. Responsibility for a distributed antenna system may be shared by multiple carriers to keep costs down.

 

The Low-Down on Log Periodic Antennas

June 23, 2016 at 8:00 AM

 

Deciding which frequency to use for your wireless application can be a downright tedious. But what if you didn’t have to choose?  What if there was an antenna that combined several frequencies into one? Log periodic antennas have that capability. Here, we’ll give you the low-down on them.

 

In the world of Wi-Fi antennas, log periodic antennas stand-out as superior multi-taskers. They are directional, wide-band, narrow-beam antennas that utilize multiple elements. They can be used for a variety of wireless applications where a wide range of frequency coverage is desired.

 

Performance-wise, the broadband characteristics of log periodic antennas allow for very good gain and directivity while operating on multiple frequencies. And because they combine several frequencies into one antenna, they eliminate the need for purchasing different antennas for each frequency, which also simplifies installation.  

 

Log periodic antennas are ideal for Distributed Antenna Systems (DAS) networks, where support for cellular, PCS and Wi-Fi communication frequencies is required. These antennas can also be used in any application that uses broadband frequencies in a wireless network.

 

Some applications include:

•  802.11a/b/g/n and 802.11ac Wi-Fi Networks

•  Distributed Antenna Systems (DAS)

•  Ultra Wide Band, UWB applications

•  Homeland Security and Public Safety Services: Fire, Police, Security

 

If you need a versatile antenna that combines multiple frequencies, a log periodic antenna may be your best bet. L-com offers several log periodic antennas and can even manufacture custom antennas to your specifications.

 

A Closer Look at PIM

January 14, 2016 at 8:00 AM

 

We’re not talking about a Personal Information Manager (PIM), or Product Information Management (PIM) or the delicious gin-based British beverage – that’s Pimm’s. The PIM we’re talking about is Passive Intermodulation, which may sound imposing, but here we’ll break it down for you.

 

What it is:

Passive Intermodulation (PIM) is a type of signal interference in a wireless system. PIM can be a problem in almost any wireless network but it can really wreak havoc on distributed antenna system (DAS) and LTE networks. DAS networks are used to distribute cellular and Wi-Fi signals throughout a building or area, and LTE networks support high-speed wireless access for mobile phones, tablets and other mobile wireless devices. With both of these technologies supporting many of our wireless devices, it has become increasingly important to detect and lessen PIM’s effects.

 

Why it happens:

PIM is caused by nonlinearities in the passive mechanical components of a wireless system such as antennas, cables and connectors, especially in places where two different metals come together. As nonlinearities increase, so do PIM signals. PIM in the transmission path degrades the quality of the wireless communication system. Damaged RF equipment or even nearby metal objects such as guy wires and anchors, roof flashing and pipes can also be sources of PIM.

 

Additionally, PIM can be caused by two or more carriers sharing the same downlink path in a wireless network. This practice is becoming more common as wireless networks become increasingly complex with multiple technologies and technology generations at a single site. When two signals combine, it causes signal interference and can significantly impact the performance of DAS and LTE networks.

 

How it's measured:

PIM is measured in decibels relative to the carrier (dBc) or decibel-milliwatts (dBm).  Levels near -100 dBm or less are generally considered good, but the lower the better.  Tests have shown that when PIM levels were increased from -125 dBm to -105 dBm there was an 18% drop in download speeds, even though 105 dBm can be considered an acceptable PIM level.


How to protect your network:

Individual components are often tested for PIM during the design and production processes to make sure that they aren’t significant PIM sources once they’re installed. In the case of a DAS, sometimes the entire system is tested for PIM as well as the individual components. Installation also plays a critical role because proper connections are necessary to keep PIM levels to a minimum.

 

PIM is also assessed during the cellular site placement process. Ideally, this happens before the cell site and antennas are positioned as well as during the installation process.

 

Plus, an increasing amount of test companies are offering specialized equipment to detect, pinpoint and address PIM sources. There are also low-PIM rated products now available to help keep PIM at bay. 

 

PIM-certified equipment is becoming more common. For example, antennas may be PIM-certified to a level of -140 dBm and those requirements are becoming increasingly strict.

With so many devices dependent on strong wireless signals, PIM could definitely throw a wrench in the system.  Fortunately, there are steps that can be taken to identify and prevent the adverse effects of PIM. 

 

Easy Answers to Your Top 5 Wireless FAQs

August 7, 2014 at 10:00 AM

 

 

If you know L-com, you know that we listen to our customers.


Over the years we have published many informative FAQs to help you get your job done. In this week’s post we have compiled our top 5 wireless FAQs to help you better understand different aspects of wireless networking, including antenna selection and operation, choosing the right WiFi amplifier for your network and more.


You’ll find that some of these FAQs are associated specifically with L-com’s products, while others are simply general knowledge that you can use and share!


 

What is a Distributed Antenna System (DAS)?

 

Often times a DAS uses RF directional couplers and/or wireless amplifiers to split and amplify a wireless signal from the source out to distributed antennas. A DAS can be designed for indoors or outdoors. This FAQ explains how a DAS system can be configured for both types of deployments. 

 

 

What is Antenna Polarity?

 

It’s simple. Click above to find out!

 

 

How do I choose the right WiFi amplifier?

 

When deciding which WiFi Amplifier to buy, there are several important options to consider: PoE, Frequency, Automatic Power Control (APC) and more. Take a look at our breakdown. 

 

 

 

 

 

How do I use a HyperLink brand Antenna?

 

Here we share some common WiFi antenna design considerations that explain which HyperLink brand antenna to use for specific wireless applications, including point-to-point and point-to-multi-point architectures.

 

Not sure which antenna is best for your application? Read on. 

 

 

Common Wireless Connectivity Terms

 

Test your knowledge of commonly used wireless terms, or refer to this extensive list when faced with a new project. Entries include Direct Sequence (DS), Effective Radiated Power (ERP), Attenuation, Wind Loading, Signal-To-Noise Ratio (SNR) and much more. 

 

© L-com, Inc. All Rights Reserved. L-com, Inc., 50 High Street, West Mill, Third Floor, Suite 30, North Andover, MA 01845