Call Detail Records (CDRs)

Author: Anagha Ravi


Telecommunications companies initially created call detail records as a billing tool. In time, however, all sorts of uses were developed for these records. For instance, businesses use them to forecast sales, track and minimize non-business call activity, determine and optimize network usage, and even identify security threats.

What is a call detail record?

Sometimes referred to as a call data record, a call detail record is a chronicle of call information, or metadata, pertaining to a particular number or user. These records contain the CDR data, such as date and time of a call; cost; duration; originating and destination numbers; whether the call was answered or not; and whether the call was outbound, inbound or toll-free. The records also show the location of cell towers connecting a call; operators can compute the approximate location of parties to a call using this cell tower location data.

Call detail records may also include metadata for text messages and cloud phone calls. However, for legal and operational reasons, these records do not log the content of calls or messages. Metadata for free services, such as the intra-Session Initiation Protocol (SIP) calls that many Voice over Internet Protocol (VoIP) providers offer, is never included in call detail records. If you need records for these services, check the ‘recent calls’ or ‘call history’ sections of your internet calling service.

Call detail record reports

Call detail record reports organize information by phone number or user, depending on what is required. Reports for a single user generally show specific metrics, such as call volume and cost, and can be very detailed. On the other hand, reports for organization phone numbers, which are typically used by entire departments, give a broad overview of calling activity.  

  • Call Master- Time, length, parties, call originator, success status of the call, file system location of call recordings, etc.
  • Call Side- Endpoint data
  • Call Events- Includes alarms, ISDN calls, sporadic echo, etc.

So, how do you get a call detail record report? If you are using a VoIP service, you can likely generate a report from the portal of your provider. You can also use call detail record tracking software, if installed.

Carriers may provide reports for certain uses, such as research, as we saw in the first section of this piece. Law enforcement officials are allowed to obtain cell phone call detail record reports, although in many countries they must have a warrant for them. In the United States, law enforcement is not required to get a warrant for the reports. 

The mechanics of call detail records 

In cellular networks, call detail records form part of the various databases and registries that network management subsystems, or NMSs, use in their operations. These operations include tracking network performance, detecting and fixing faults, and keeping network components up to date. As we saw earlier, call detail records are primarily used for billing.

The process of generating metadata for calls or other communications so that your phone company can determine what to charge you involves a number of steps. First, your phone – ‘user equipment,’ in the argot of the telecommunications world – transmits a radio signal to the closest cell towers when you tap ‘call’ or ‘send.’ These towers are also known as Base Transceiver Stations (BTSs), or simply base stations.

For easy management, individual BTSs are grouped into a location area (LA), each with a unique identifier known as a location area code (LAC). The LAC is used to keep track of the location of mobile phones so that the network knows where to route incoming calls. All BTSs within an LA are monitored and managed by a base station controller, or BSC. The BSC ensures that you’re seamlessly handed over from one BTS to the next when you are on the move.

The BSC links BTSs with mobile switching centers, MSCs, which set up, route and release calls; route text messages, faxes and conference calls; connect to the public switched telephone network, or PSTN; and handle inter-BSC and inter-MSC handovers. All mobile phone calls, whether to landlines or other cell phones, must pass through these switching centers. MSCs are a critical building block of the network management subsystems (NMSs) we looked at earlier.

Call detail records do not chronicle all these steps. This is because only the information that MSCs send to the NMSs is logged; the rest is discarded. For this reason, these records do not show the identity of every BTS through which your calls were routed, for example; only the towers to which you and the recipients were directly connected at the time you were communicating are shown.

Business use cases for call detail records 

1. Reducing Costs of Communication
Businesses can use call detail records to cut communication costs. For instance, you can quickly find out which trunks and extensions are unused and eliminate them. You can also determine if your voice and data networks are fully utilized or not, and adjust your budget accordingly. These records can also help you ferret out and minimize non-business related communication.

2. Making Planning Easier 
Call detail records contain information that can help you uncover patterns in your business communication, which can make planning considerably easier. For instance, these records may show that certain departments engage with customers more often at certain times of the week, allowing you to forecast where and when to allocate resources.

3. Helping Uncover Security Threats and Fraud 
These records can help you uncover usage patterns that deviate from the norm. Network administrators can then flag and investigate such activity, sometimes using machine learning.

4. Evaluating Usage Patterns 
Telecommunications firms can extract a great deal of useful usage pattern data from call detail records. For instance, it is possible to uncover usage patterns by demographic, which can be helpful if there are plans to develop services or offer incentives targeted at a particular group. Usage analysis can also reveal opportunities to maximize revenue.

Non-business use cases 

This innovative use of call detail records is not limited to the business world. In Côte d’Ivoire, researchers used a call detail record dataset provided by a local subsidiary of French telecommunications giant Orange to devise a way of reducing traffic congestion and travel time in Abidjan, the country’s capital. The researchers were even able to determine poverty levels for 11 regions across the country using the same dataset, a task that would have required substantial time, legwork and cash had it been done the usual way.

These records have been leveraged to improve the efficiency of relief efforts in Haiti after the 2010 earthquake, keep track of public response to government health advisories in Mexico during the 2009 swine flu epidemic, monitor post-disaster population movements in New Zealand after the 2011 earthquake, and map multiple malaria outbreaks in Kenya. They are also widely used in criminal prosecutions in the United States, albeit not without controversy.

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