CCM-PSTN Access for Your Contact Center

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CC Expertise M Customer Care Management Just in time!! Knowledge and skills for the customer support professional PSTN Access for Your Contact Center Telephone Lines The telephone lines that connect your call center to the rest of the world are often the first link in a long chain of factors that affect the perceived service level received by your customer. It doesn’t matter how much you spend on a CRM package if customers receive a busy signal when they try to call you. This article origin
  Telephone Lines The telephone lines that connect your call center to the rest of the world are often the firstlink in a long chain of factors that affect the perceived service level received by yourcustomer. It doesn’t matter how much you spend on a CRM package if customers receive abusy signal when they try to call you. This article srcinally appeared in Business Communications Review, December 2003 issue pp.36-41. Updated September 2006 to reflect IP Telephony issues.   M CC Expertise PSTN Access for Your Contact Center   Customer Care Management Just in time!!Knowledge and skills for the customer support professional    Page 1    M CC Expertise Copyright Ike Mitchell 2007 PSTN Access for your Contact Center   The telephone lines that connect your callcenter to the rest of the world are often thefirst link in a long chain of factors that affectthe perceived service level received by yourcustomer. It doesn’t matter how much youspend on a CRM package if customers receivea busy signal when they try to call you. All too often, public switched telephonenetwork (PSTN) access is simply ordered, withlittle or no thought as to how it dovetails withbusiness objectives. However, there are manytechniques and options available to set up yourPSTN access arrangements. The ultimate goalof PSTN access engineering is to provideadequate (in terms of capacity), reliable andcost effective transport for telephone callsbetween the public telephone network andyour premise. PSTN Access Sizing “Adequate” means that the bandwidth (or invoice parlance, the number of simultaneoustwo-way voice communication channels) is bigenough to ensure that callers get through toyour call center. It is impossible to put inenough trunks (see Table 1 – Glossary   ) toensure 100 percent of inbound calls get intoyour automatic call distributor (ACD) at will.Disasters, marketing and dozens of otherfactors can drive unanticipated traffic loadsinto your center.The most common measure/metric used foraccess sizing is blockage rates. When callcenter executives say they have a 5 percentblockage rate, they usually mean that 5percent of callers receive a busy signal over thereporting period. When sizing PSTN access,however, engineers usually use a Grade of Service (GOS). A 5 percent GOS means thatduring the busy hour of the busy day of thebusy month, 5 percent of callers receive a busysignal.This should result in a very small number of busy signals over the reporting period - andthose only occurring during the busiest hoursof the planning period.Busy signals are difficult to measure. All ACDs have All Trunks Busy (ATB) reports.But be careful when examining ATB reports,because they only record the number of timesor the percent of time all trunks are busy. Toget a better picture of the busy signalsituation, it is necessary to go to the localexchange carriers (LEC) and interexchangecarrier (IXC).IXCs can readily supply a blocked call reportand it can usually be counted upon to beaccurate. LECs, on the other hand, usuallydon’t charge on a call-by-call basis like theIXCs so it is much more difficult to get thisreport from a LEC. The report must berequested in advance, and the ILEC willcollect the information on the specified linesfor the specified period of time. Even then, theanalyst should inspect the results carefully foraccuracy.However, these blocked call reports provideonly limited help in assessing the true loss of demand experienced because of networkblockage. To drill deeper, you’ll need goodanalyst with some basic databaseprogramming skills. This person can do ansrcinating-phone-number sort to identify, outof all the blocked calls, how many came fromunique callers. This will help you produce areport that takes into account the propensityof callers to redial repeatedly until they finallyreach a customer service representative (CSR).The above discussion on analyzing busysignals and caller retry behavior demonstratesthe folly of under-trunking — i.e., notproviding enough telephone trunk access.Undertrunking hides the true demand, and, assuch, will make it difficult to justify realisticstaffing requirements to senior managers. A common tactic used by call center managersis to take telephone trunks in and out of service to manage service level, preferring togive callers a busy signal rather than a lowservice level. This is a legitimate strategy inknown understaffing situations or inmarketing promotions that serve only togarner attention rather than offer any true    Page 2    M CC Expertise Copyright Ike Mitchell 2007 sale or service (the $99 round trip air farearound the world, for example) But thispractice should be used sparingly. When donepurposefully to improve service level, the callcenter manager must let senior managementknow they are engaging in this practicebecause it can be perceived as dishonest. Thisis especially true if a bonus is paid out onservice level goals.  Access Configuration One of the most common mistakes made inaccess engineering isprovisioning multiple trunkgroups to the toll free carrier. Inpractice, a call center only needs one trunkgroup to an IXC. If there is a largeadministrative function in the building, theremay be an argument for having separateoutbound toll and inbound toll-free trunkgroups to ensure outbound capacity remainsavailable at all times. ISDN trunks can beconfigured to reserve a specified amount of capacity for outbound service, thus eliminatingthe need for the separate in and out trunkgroups.In many call centers, the policy is that eachnew phone number, client or product added tothe center receives its own telephone lines. Therationale for this practice is either reservedcapacity, cost allocation or reporting.standard feature on all ACDs, and even themost basic reporting package can report onDNIS signaling.In truth, there is no justification for thisapproach, and segmented trunks are highlyinefficient. Callers can be receiving busysignals on one trunk group while circuits sitidle in other trunk groups. Dialed NumberIdentification Service (DNIS), which reportsthe phone number that the caller dialed, is aMost ACDs can be configured to placemaximums on simultaneous calls on any DNISnumber, and ISDN allows even more controlover capacity allocation. Traffic Engineering So how many telephone trunks are required fora given number of CSRs? Old adages such as“one and a half telephone lines per CSR”oversimplify line sizing. The basic metricsrequired to determine line size are: ãNumber of callsãLength of time a call occupies a circuit.Together these yield a total base demand foraccess service. As noted earlier, this isusually calculated for the busiest hour overthe planning period. To account for therandom arrival of calls, this is applied to astatistical model to ascertain the number of trunks required for the call center.So the number of calls is simple enough. Butpoint #2 above, “Average Trunk HoldingTime” (ATHT) is a bit more complex and isdefined as:Talk time and forced announcements(automated attendants are included in this)are straight forward, but ring time and queuetime require some thought. Ring Time — Ring time is usually betweenzero and 12 seconds. Ring time can be set onthe ACD to allow as many ring cycles asdesired (a ring cycle usually lasts six seconds — two of ringing and four of silence. The“Ring Cycle” is also the name of a Germanopera that lasts 16 hours and seems evenlonger.)It is unwise to set the ring time to zero,because callers will feel obligated to tell theCSRs that they did not hear any ring tones,thereby increasing talk time. Trunksprovisioned as ISDN (discussed later, seeglossary) have no ring time, in that ringsignaling is done on the D-channel.Traditional T1s then should be sized withabout six seconds of ring time (again, checkyour switch setting for this). ISDN PRIsshould be sized with zero ring time includedin the ATHT metric. Queue Time  — Queue time is a difficultmetric to quantify. Goals are fine, but it isnecessary to engineer to reality. Also, therecan be a philosophical discussion as to howmuch queue time should be allowed based onwhether the call center is a revenue center or ATHT = Ring time + Talk time + Forced announcements + Queue Time       Page 3    M CC Expertise Copyright Ike Mitchell 2007 not. The theory is: In a revenue center, youwant callers to hold on as long as possible toreach a CSR, so as to capture as much reve-nue as possible. That said, one would neveruse predictive queuing (see glossary) in arevenue center, because predictive queuingtends to increase “abandon early on” in thequeue. In contrast, callers who don't knowhow long the queue is, combined with snappyon-hold music and messages, can hold quitelong without realizing how much time haspassed.In short, a revenue center should significantlyover-trunk to limit the amount of lost revenue.Proper staffing is the first remedy, of course.But it isn’t possible or economical to never beunderstaffed. So there will always be periodsof time where queues are longerthan desired.The cost of telephone trunks istrivial in comparison to the po-tential revenue lost. Some simplemath will demonstrate that theincreased revenue resulting fromincreased queue time can pay forthe incremental line and per-minute charges.Let’s say that an additional T1/PRI will allowa center to handle an additional 100 calls in anhour. That T1/PRI will cost, say, $1,000 permonth. If the net revenue per call is $100, only10 additional sales are needed to justify theadditional access service. If the customer buyrate is 10 percent, the additional costs can berecovered in a single hour. The center will cap-ture additional calls and revenue in more thana single hour, so the benefits seem obvious.On the service side, there is no revenue todrive over-trunking. However, it is a well-understood phenomenon that talk time beginsto increase as queue time passes a certainthreshold. Callers begin to complain about thewait. This drives up both access line costs andpersonnel costs. In effect, you pay extra to de-liver bad service. It is this threshold queuelength that service call centers want to use astheir queue time in the calculation of ATHT. Statistical Modeling The decision to use Poisson, Erlang B, Ex-tended Erlang B or some simulation model isthe subject of much academic debate. It is,however, academic. As you engineer to betterand better service, these models approach oneanother. If you are engineering for, say, a 5-percent GOS in the busy hour of the year,there will be little difference in results be-tween the various engineering approaches.Because Extended Erlang B accounts for retrybehavior, in theory, it might be an appropriatemodel for an inbound call center.But again, in this world of T1 and PRI high-capacity digital services that come in 24- and23-voice-connection increments respectively, itrarely matters. Most engineers use Erlang Bbecause MS Excel add-ins are readily availableand they generally round up tothe next full T1/PRI.In short, access is cheap. Erroron the side of over capacity. It iseasy to take circuits out of ser-vice, but difficult and time con-suming to add circuits. Reliability High-capacity digital access services are highlyreliable. There are, however, very few call cen-ters that have not experienced an access fail-ure in the last 24 months. While the probabil-ity for disaster is small, the impact of a PSTNaccess failure is devastating. So spending sometime developing contingency plans is worth theeffort. (Switched access service is not discussedhere because it is uncommon and expensive,even for the smallest operations.) A call center reaches the PSTN via either alocal (LEC) or a long distance (IXC) service, orboth. The most common arrangement, espe-cially in large cities, is to have a set of trunksfor local service and a separate set for long dis-tance. A center almost always has some localservice for administrative purposes, most oftenDirect Inward Dial (DID)/Direct Outward Dial(DOD), that lets administrative personnelhave their own phone number without havingto dedicate specific lines to reach individuals. The cost of telephone trunks istrivial in comparisonto the potentialrevenue lost.
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