Brief explanation on how Search Engine works

As more people prefers to search for information on the internet, the internet search engines have become an important part to business marketing. There are various search engines available, like Google, Yahoo, MSN, etc. The most popular one of course is Google, so this article would focus mainly on the Google search engine.

 

What happens when a user do an organic search:
• The Search Engine first analyze the words the searcher typed in and pick the pages that match those words
• It will then ranks the matches.
• Finally it displays the search results.

 

How Search Engines Find web pages for the organic indexes
• Search Engine Spider traverses the internet via hyperlinks
• The spider visits each HTML page and scoops up all the text on the page, assigning the page a unique document number
• The Search Engine then removes the tags, keeping only the text
• Finally the search index is created with each keyword stored along with information about what pages it was found on

So the Index table will look something like that:

se1 And the document table will look something like that:

se2
Ranking the Matches

So after the Search Engine retrieve the pages (from the Index table) that match the search phrase which the user want to search for, it will rank these pages according to the following criteria:
Keyword Density – How frequently the search keywords are found in those pages
Keyword Proximity – Whether the search terms in a query are found close to each other in the web page.
Keyword Prominance – Pages that feature query words in titles, headings, emphasized text and initial paragraphs are said to have high keyword prominance.
Link Popularity – How many sites are linked to the page, and the authority of the sites that linked to the page.

 

Understanding how the search engine works is the first step towards SEO (Search Engine Optimization). In order for your site to rank high in search engine for your preferred keywords/keyphrases, you would have to optimize your webpages accordingly.

However, do bear in mind that, ultimately your webpages are meant to be read by humans, not machines. So do not cluster your webpages with keywords as that would become unreadable and google doesn’t like that too. Lastly, do note that google’s algorithm changes regularly so SEO is a continuous instead of one-off effort.

Basic Components of Cellular Systems

There are various cellular systems in the world, such as the GSM and CDMA. The design of these cellular systems are complicated but the architecture of most cellular systems can be broken down into six basic components.

In this article, I will illustrate the six basic components that can be found in most cellular systems.

 

Six basic components of Cellular Systems
The architecture of most cellular systems can be broken down into the following six components:

• Mobile Station (MS)
A mobile station is basically a mobile/wireless device that contains a control unit, a transceiver and an antenna system for data and voice transmission. For example, in GSM networks, the mobile station will consist of the mobile equipment (ME) and the SIM card.

• Air Interface Standard
There are three main air interface protocols or standards: frequency division multiple access (FDMA), time division multiple access (TDMA) and code division multiple access (CDMA). These standards are basically the medium access control (MAC) protocols that define the rules for entities to access the communication medium.

These air interface standards allow many mobile user to share simultaneously the finite amount of radio channels.

• Base Station (BS)
A base station is a fixed station in a mobile cellular system used for radio communications with mobile units. They consist of radio channels and transmitter and receiver antenna mounted on a tower.

• Databases
Another integral component of a cellular system is the databases. Databases are used to keep track of information like billing, caller location, subscriber data, etc. There are two main databases called the Home Location Register (HLR) and Visitor Location Register (VLR). The HLR contains the information of each subscriber who resides in the same city as the mobile switching center (MSC). The VLR temporarily stores the information for each visiting subscriber in the coverage area of a MSC. Thus, the VLR is the database that supports roaming capability.

• Security Mechanism
The security mechanism is to confirm that a particular subscriber is allowed to access the network and also to authenticate the billing.

There are two databases used for security mechanism: Equipment Identify Register (EIR) and Authentication Center (AuC). The EIR identifies stolen or fraudulently altered phones that transmit identity data that does not match with information contained in either the HLR or VLR. The AuC, on the other hand, manages the actual encryption and verification of each subscriber.

• Gateway
The final basic component of a cellular system is the Gateway. The gateway is the communication links between two wireless systems or between wireless and wired systems. There are two logical components inside the Gateway: mobile switching center (MSC) and interworking function (IWF).

The MSC connects the cellular base stations and the mobile stations to the public switched telephone network (PSTN) or other MSC. It contains the EIR database.

The IWF connects the cellular base stations and the mobile stations to Internet and perform protocol translation if needed.

 

Conclusion
This article aims to provide an introductory guide to the architecture of a typical cellular system and identify the six basic components found in most cellular systems. This article offers an insight towards how a cellular system is designed although different cellular systems may have variations in their own implementations.

Introduction to Short Message Service (SMS)

Short Message Service (SMS) is the technology that enables user to send and receive text messages via mobile phones. It supports alphanumeric message up to 160 characters, by packing the 7-bit ASCII characters into 8-bit octets. Message can be typed directly using cellular phones or via other interfaces such as computers.

 

SMS Service Types

There are two basic types of SMS:

• Point-to-point communication
Point-to-point communication service is the service that supports messages between two subscribers of the SMS services. This is the service type that is used by normal individual subscribers.

• SMS cell broadcast service (SMSCB)
SMS cell broadcast service is the type of service whereby the same message is broadcast to multiple SMS subscribers. Such service is only available to the network operators, and is normally used for messages like weather alerts and news reports.

 

SMS Network Architecture

SMS network architecture is based on the architecture of Global System for Mobile Communications (GSM).

SMS is a store and forward data services. This means that messages are not sent to the destination directly. Instead, messages are routed and stored in SMS Message Centre (SMSMC), and then forwarded to the destination.

An SMSMC provides a number of services, including the regulation and transfer of text messages between mobile phones. When a subscriber sends a text message to a recipient, the mobile phone actually sends the message to the SMSMC. The SMSMC stores the message and then delivers it to the designated recipient when they are available. The SMSMC usually has a configurable validity period that determine how long it will store the message, and the user can usually specify a shorter validity period if they want.

In addition to regulation of messages, the SMSMC also handles any charging that needs to take place. In general, there is at least one SMSMC per network.

 

Conclusion
This article aims to provide an introductory guide to the Short Message Service (SMS) which is part of the GSM specification. The limit in size of SMS is 160 characters if purely Latin alphabets are used. If non Latin alphabets such as Chinese characters are used, the limit will be 70 characters.